COMPOSITE CERAMICS WITH LOW DIELECTRIC LOSSES

Abstract

A ceramic composite material includes Barium titanate (BaTiO.sub.3) and CoFe.sub.1.98Nb.sub.0.02O.sub.4. The BaTiO.sub.3 is present in an amount of 1 to 99 percent by weight based on the total weight of the BaTiO.sub.3 and the CoFe.sub.1.98Nb.sub.0.02O.sub.4. The CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of 1 to 99 percent by weight based on the total weight of the BaTiO.sub.3 and the CoFe.sub.1.98Nb.sub.0.02O.sub.4. These composite products may be suitable for high-frequency electromagnetic device applications.

Claims

1: A ceramic composite material, comprising: BaTiO.sub.3; and CoFe.sub.1.98Nb.sub.0.02O.sub.4, wherein the BaTiO.sub.3 is present in an amount of 1 to 99 percent by weight based on a total weight of the BaTiO.sub.3 and the CoFe.sub.1.98Nb.sub.0.02O.sub.4, wherein the CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of 1 to 99 percent by weight based on the total weight of the BaTiO.sub.3 and the CoFe.sub.1.98Nb.sub.0.02O.sub.4.

2: The material of claim 1, wherein the BaTiO.sub.3 is in the form of particles having a crystallite size of 20 to 45 nm.

3: The material of claim 2, wherein a BaTiO.sub.3 phase is present as a single phase with a tetragonal structure.

4: The material of claim 1, wherein the CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in the form of particles having a crystallite size of 5 to 50 nm.

5: The material of claim 4, wherein a CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase is present as a single phase.

6: The material of claim 1, wherein the BaTiO.sub.3 and the CoFe.sub.1.98Nb.sub.0.02O.sub.4 are present as separate phases.

7: The material of claim 1, wherein the BaTiO.sub.3 is a cubic phase.

8: The material of claim 1, having a porous, irregular granular morphology with an average particle size of 0.1 to 10 m.

9: The material of claim 2, wherein a BaTiO.sub.3 phase comprises spherical particles with an average particle diameter of 0.1 to 2 m.

10: The material of claim 4, wherein a CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase comprises rhombic particles with an average particle diameter of 0.5 to 5 m.

11: The material of claim 1, wherein the ceramic composite material has one or more regions of a BaTiO.sub.3 phase and one or more regions of a CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase.

12: The material of claim 1, wherein the ceramic composite material is biphasic comprising a dielectric BaTiO.sub.3 phase and a magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase.

13: The material of claim 1, wherein barium is present in an amount of 10 to 30 mol percent, titanium is present in an amount of 10 to 30 mol percent, oxygen is present in an amount of 40 to 60 mol percent, cobalt is present in an amount of 0.1 to 3 mol percent, iron is present in an amount of 0.1 to 4 mol percent, and niobium is present in an amount of 0.1 to 2 mol percent based on a total number of mols of the barium, titanium, oxygen, cobalt, iron, and niobium.

14: The material of claim 1, having a dielectric constant of 1 to 20 at a frequency of 1 to 10.sup.6 Hz.

15: The material of claim 1, having a dielectric loss of 0.1 to 7 at a frequency of 1 to 10.sup.6 Hz according to ASTM D150.

16: The material of claim 1, having a dielectric loss tangent of 0.01 to 1 at a frequency of 1 to 10.sup.6 Hz.

17: The material of claim 1, wherein the BaTiO.sub.3 is made by a sol-gel process.

18: The material of claim 1, wherein the CoFe.sub.1.98Nb.sub.002O.sub.4 is made by a hydrothermal process.

19: The material of claim 1, wherein the ceramic composite material is made by a solid-state reaction process.

20: A high frequency device, comprising: the material of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] A more complete appreciation of embodiments of the present disclosure (including alternatives and/or variations thereof) and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description of the embodiments when considered in connection with the following drawings, in which:

[0034] FIG. 1 shows X-ray diffraction (XRD) patterns of (100-x) % BaTiO.sub.3 (BTO)+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%, 2%, 5%, 10%, 20%, and 100%) and reference cards of different phases, according to certain embodiments;

[0035] FIG. 2 shows variations of crystallite size (D.sub.XRD) values for both BTO and CoNb.sub.0.02Fe.sub.1.98O.sub.4 phases with respect to x content, according to certain embodiments;

[0036] FIG. 3A shows a scanning electron microscopy (SEM) image for 100% BTO+0% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0037] FIG. 3B shows an SEM image for 98% BTO+2% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0038] FIG. 3C shows an SEM image for 95% BTO+5% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0039] FIG. 3D shows an SEM image for 90% BTO+10% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0040] FIG. 3E shows an SEM image for 80% BTO+20% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0041] FIG. 4 shows elemental mapping images for 90% BTO+10% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0042] FIG. 5A shows Energy dispersive X-ray spectroscopy (EDX) spectra and corresponding atomic ratios (insets) for pure BTO sample, according to certain embodiments;

[0043] FIG. 5B shows EDX spectra and corresponding atomic ratios (insets) for 90% BTO+10% CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite, according to certain embodiments;

[0044] FIG. 6 shows variations in dielectric constant () with frequency () for pure BTO (inset figure x=0.0) and (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=2%, 5%, 10%, 20% and 100%) measured at room temperature, according to certain embodiments;

[0045] FIG. 7A shows variations in dielectric loss () with of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%), according to certain embodiments;

[0046] FIG. 7B shows variations in with of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=2%, 5%, 10%, and 20%), according to certain embodiments;

[0047] FIG. 7C shows variations in with of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=100%), according to certain embodiments;

[0048] FIG. 7D shows variations in for different x contents (x=0%, 2%, 5%, 10%, 20%, and 100%) measured at =1 Hz, according to certain embodiments;

[0049] FIG. 8 shows variations in dielectric loss tangent (tan ) with for different (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%, 2%, 5%, 10%, 20%, and 100%) measured at room temperature, according to certain embodiments;

[0050] FIG. 9A is a Cole-Cole plot showing the range of impedance spectra for curves of an imaginary part of impedance (Z) versus real part of impedance (Z) for (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%, 2%, 5%, 10%, 20%, and 100%), according to certain embodiments;

[0051] FIG. 9B is a Cole-Cole plot showing an expanded view of impedance spectra at a lower frequency for curves of Z versus Z for (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%, 2%, 5%, 10%, 20%, and 100%), according to certain embodiments;

[0052] FIG. 10A shows the electrical modulus plane plots of the imaginary part of modulus (M) versus real part of modulus (M) of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%) measured at room temperature, according to certain embodiments;

[0053] FIG. 10B shows the electrical modulus plane plots of M versus M of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=2%), measured at room temperature, according to certain embodiments;

[0054] FIG. 10C shows the electrical modulus plane plots of M versus M of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=5%), measured at room temperature, according to certain embodiments;

[0055] FIG. 10D shows the electrical modulus plane plots of M versus M of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=10%), measured at room temperature, according to certain embodiments;

[0056] FIG. 10E shows the electrical modulus plane plots of M versus M of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=20%), measured at room temperature, according to certain embodiments; and

[0057] FIG. 10F shows the electrical modulus plane plots of M versus M of (100-x) % BaTiO.sub.3+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=100%), measured at room temperature, according to certain embodiments.

DETAILED DESCRIPTION

[0058] In the following description, it is understood that other embodiments may be utilized, and structural and operational changes may be made without departure from the scope of the present embodiments disclosed herein.

[0059] When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0060] Embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all, embodiments of the disclosure are shown.

[0061] Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be constructed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims. Further, as used herein, the words a, an and the like generally carry a meaning of one or more, unless stated otherwise.

[0062] Furthermore, the terms approximately, approximate, about, and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.

[0063] The use of the terms include, includes, including, have, has, or having should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

[0064] As used herein, particle size may be thought of as the length or longest dimension of a particle.

[0065] A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. For example, if a particular element or component in a composition or article is said to have 5 wt. %, it is understood that this percentage is in relation to a total compositional percentage of 100%.

[0066] As used herein, composite material or composites refers to a combination of two or more constituent materials with distinct physical and chemical properties. The constituent materials may have notably dissimilar chemical or physical properties that, when merged, produce the composite material with properties unlike the individual materials. Within the composite material, the constituent materials remain separate and distinct, which distinguish composites from mixtures and solid solutions.

[0067] As used herein, nanoparticles are particles having a particle size of 1 to 500 nm within the scope of the present disclosure. The nanoparticles may exist in various nanomaterial shapes, such as nanowires, nanocrystals, nanorectangles, nanotriangles, nanopentagons, nanohexagons, nanoprisms, nanodisks, nanocubes, nanoribbons, nanoblocks, nanobeads, nanotoroids, nanodiscs, nanobarrels, nanogranules, nanowhiskers, nanoflakes, nanofoils, nanopowders, nanoboxes, nanostars, tetrapods, nanobelts, nano-urchins, nanofloweres, the like, and mixtures thereof.

[0068] As used herein, a ceramic refers to an inorganic non-metallic solid constructed of either metal or non-metal compounds, such as metallic oxide, inorganic, nitride, and/or carbide material. which have been shaped and then hardened via heating at high temperatures. Ceramics are hard, brittle, strong in compression, and weak in shearing and tension. Ceramics can withstand high temperatures and chemical corrosion caused by acidic and caustic environments and the like.

[0069] As used herein, magnetic materials refers to materials that produce a magnetic field in response to an applied magnetic field (also referred to as magnetism) or get impacted by external electromagnetic fields in their surroundings. The overall magnetic behavior of magnetic materials may vary depending on structure of the material, the electronic configuration, and the like. Types of magnetic material may include ferromagnetic materials, ferrimagnetic materials, paramagnetic materials, diamagnetic materials, and the like.

[0070] As used herein, ferromagnetic materials refers to materials that demonstrate a spontaneous net magnetization at an atomic level despite the absence of an external magnetic field, and the materials acquire permanent magnetism. Ferromagnetic materials may have unpaired electrons. Intrinsic magnetic moments of the unpaired electrons in the ferromagnetic material have tendency to be parallelly aligned in an applied magnetic field as well as a magnetic moment tendency to orientate parallel to one another in the absence of an applied magnetic field to maintain a lowered energy state. Ferromagnetic materials may have a crystalline structure and/or a microstructure to achieve ferromagnetism.

[0071] As used herein, ferroelectric property refers to a property of some materials for having a spontaneous polarization that can be reversed by the function of an external electric field. Materials with ferromagnetic and ferroelectric properties are multiferroic.

[0072] As used herein, paraelectric property refers to the capability of certain materials (specifically ceramic crystals) to become polarized under an applied electric field. Materials with paraelectric properties may have no dipoles without the presence of an electric field. Materials with paraelectric properties may form dipoles and show polarization when an electric field is applied, which may disappear when the electric field is removed.

[0073] As used herein, dipole refers to a pair (2) of equal and oppositely charged or magnetized poles separated by a distance.

[0074] As used herein, piezoelectricity refers to electric polarization that is resultant of mechanical stress, such as pressure and latent heat. Piezoelectricity is the electric charge that accumulates in solid materials, such as crystals, ceramics, and the like, in response to applied mechanical stress.

[0075] As used herein, a dielectric constant, also referred to as relative permittivity or permittivity, refers to a measure of a substance for storing electrical energy in an electric field. It is the ratio of the permittivity of a material or substance to the permittivity of free space or a vacuum.

[0076] As used herein, sol-gel process refers to method for producing solid materials from small molecules. The chemical synthesis method for producing materials, including resins, where an oxide network is developed through at least polycondensation reactions of a molecular precursor in a liquid. In the present case, the molecular precursors are the silane derivatives (alkoxysilanes). The sol-gel process is a wet-chemical technique that may be used for the fabrication of glassy and ceramic materials, and the like. In the chemical procedure, a sol (colloidal solution) is formed and gradually transitions towards the formation of a gel-like diphasic system, which contains and liquid and a solid phase. These phases comprise morphologies ranging from discrete particles to continuous polymer networks and the like. Removal of the remaining liquid or solvent phase may require a drying process, which may result in the shrinkage and densification of the material. A thermal treatment may be used for further polycondensation. The properties of a sol-gel material may be influenced by variation in the drying process and thermal treatment. The finished product of a sol-gel synthesis process can be referred to as a sol-gel material, a sol-gel processed material, a sol-gel product, or a sol-gel processed product.

[0077] As used herein, a hydrothermal process refers to a process in which a nanomaterial synthesis is dependent on the solubility of the reaction species in a water medium at a desired pressure. The hydrothermal process may include various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures. The hydrothermal process may also be referred to as a hydrothermal synthesis or hydrothermal method.

[0078] As used herein, crystallites refers to small (generally microscopic) crystals that are bonded together by boundaries that are substantially irregular, including polycrystalline solids. Crystallites may form during the cooling of materials.

[0079] Aspects of the present disclosure are directed to composite materials of BaTiO.sub.3 (BTO) and CoFe.sub.1.98Nb.sub.0.02O.sub.4. Magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 and dielectric BTO phases were initially prepared via sol-gel and hydrothermal methods, respectively. Next, diverse materials of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 (x=0, 2, 5, 10, 20, and 100%) were developed using a solid-state reaction. The development of biphasic materials is confirmed through X-ray diffraction (XRD) and energy dispersive X-rays (EDX) analyses. Scanning electron microscope (SEM) observations indicated the existence of dissimilar particles in terms of shape and size, which belong to CoFe.sub.1.98Nb.sub.0.02O.sub.4 and BTO phases. The variations in dielectric constants and loss tangents were also investigated at ambient temperature in a frequency range of 10.sup.0 to 10.sup.6 Hz. Low values of dielectric loss tangent less than 1 are observed for different composites (i.e., x=2, 5, 10, and 20%). More specifically, composite materials with x5% displayed very low dielectric loss tangent (below 0.1), along with good stability over the entire frequency range. The obtained results indicated that these composite products could be suitable for high-frequency electromagnetic device applications.

[0080] Embodiments of the present disclosure relate to ceramic composite materials that include BaTiO.sub.3 (BTO) and CoFe.sub.1.98Nb.sub.0.02O.sub.4. BTO belongs to the family of perovskites oxides (ABO.sub.3), and it is a compound with ferroelectric properties and a high dielectric constant. It is a ferroelectric prototype that goes through a sequential crystal structure shift with temperature from ferroelectric to the paraelectric phase. The dielectric, ferroelectric, and piezoelectric properties of BTO as a multifunctional perovskite ceramic material have applications in diverse fields, such as thermostats, thermistors, multilayer ceramic capacitors, sensors, energy storage devices, energy conversion technologies, catalysis, biomedical applications, and the like.

[0081] In an embodiment, the BTO is present in an amount of 1-99%, preferably 5-98, preferably 10-95, preferably 15-90, preferably 20-85, preferably 25-80, preferably 30-75, preferably 35-70, preferably 40-65, preferably 45-60% by weight based on the total weight of the BTO and the CoFe.sub.1.98Nb.sub.0.02O.sub.4. In a specific embodiment, BTO is present in an amount of about 98% by weight. In another embodiment, BTO is present in an amount of about 95% by weight. In another embodiment, BTO is present in an amount of about 90% by weight. In yet another embodiment, BTO is present in an amount of about 80% by weight.

[0082] In some embodiments, particles in a BTO phase have a crystallite size of 20-45 nm, preferably 21-44, preferably 22-43, preferably 23-42, preferably 24-41, preferably 25-40, preferably 26-39, preferably 27-38, preferably 28-37, and preferably 29-36 nm. In a preferred embodiment, the crystallite size of pure BTO is about 36.8 nm. In some embodiments, the BaTiO.sub.3 phase includes spherical particles with an average particle diameter of 0.1-2 m, preferably 0.2-1.9, preferably 0.3-1.8, preferably 0.4-1.7, preferably 0.5-1.6, preferably 0.6-1.5, preferably 0.7-1.4, preferably 0.8-1.3, preferably 0.9-1.2, and preferably 1.0-1.1 m. In some embodiments, the BTO phase is present as a single phase with a tetragonal structure, indicating the creation of single-phase ferroelectric BaTiO.sub.3 perovskite. In some embodiments, the BTO phase in the ceramic material includes spherical particles with a high density of pores. In some embodiments, the BTO phase in the ceramic material includes spherical particles with a tetragonal structure. In some other embodiments, the BTO phase in the ceramic material includes spherical particles with a cubic phase. Numerous methods, such as co-precipitation, hydrothermal, sol-gel methods, are known in the art of preparing the BTO. In a preferred embodiment, BTO is made by a sol-gel process.

[0083] The composite also contains CoFe.sub.1.98Nb.sub.0.02O.sub.4, which is a Nb-based cobalt ferrite. The d.sup.0 configuration of Nb leads to a linear magnetoelectric coefficient at ambient temperature, which may be used for magnetoelectric sensors, memory storage devices, and the like. The CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of 1-99%, preferably 2-95, preferably 5-90, preferably 10-85, preferably 15-80, preferably 20-75, preferably 25-70, preferably 30-65, preferably 35-60, preferably 40-55% by weight based on the total weight of the BTO and the CoFe.sub.1.98Nb.sub.0.02O.sub.4. In a specific embodiment, CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of about 2% by weight based. In another embodiment, CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of about 5% by weight. In another embodiment, CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of about 10% by weight. In yet another embodiment, CoFe.sub.1.98Nb.sub.0.02O.sub.4 is present in an amount of about 20% by weight.

[0084] In some embodiments, particles in a CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase have a crystallite size of 5-50 nm, preferably 6-49, preferably 7-48, preferably 8-47, preferably 8-46, preferably 10-45, preferably 11-44, preferably 12-43, preferably 13-42, preferably 14-41, preferably 15-40, preferably 16-39, preferably 17-38, preferably 18-37, preferably 19-36, preferably 20-35, preferably 21-34, preferably 22-33, preferably 23-32, and preferably 24-31 nm. In a preferred embodiment, the crystallite size of CoNb.sub.0.02Fe.sub.1.98O.sub.4 is about 10.6 nm. In some embodiments, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase is present as a single phase with a cubic spinel structure. In some embodiments, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase includes rhombic particles with an average particle diameter of 0.5-5 m, preferably 0.5-4.5, preferably 1-4, preferably 1.5-3.5, preferably about 2-3 m. In some embodiments, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 is made by a hydrothermal process.

[0085] In some embodiments, the ceramic composite material is made by a solid-state reaction process. In some embodiments, the BTO and the CoFe.sub.1.98Nb.sub.0.02O.sub.4 are present as separate phases in the ceramic composite material. In an embodiment, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase is present as a cubic spinel structure in the ceramic composite material. In an embodiment, the BTO is a cubic phase ceramic composite material. In certain other embodiments, the BTO is in a tetragonal phase ceramic composite material. In a certain embodiment, the BTO in the ceramic composite material may exist in both the tetragonal and cubic phases, with the cubic phase being the predominant phase. In some embodiments, more than 50%, preferably 60%, preferably 70%, preferably 80%, preferably 85%, preferably 90%, preferably 95%, preferably 96%, preferably 97%, preferably 98%, and preferably 99% of BTO exists in the cubic phase in the ceramic composite material.

[0086] In some embodiments, the ceramic composite material has a porous, irregular granular morphology with an average particle size of 0.1-10 m, preferably 0.5-9.5, preferably 1-9, preferably 1.5-8.5, preferably 2-8, preferably 2.5-7.5, preferably 3-7, preferably 3.5-6.5, preferably 4-6, and preferably 4.5-5.5 m. In some embodiments, the ceramic composite material has one or more regions of a BaTiO.sub.3 phase and one or more regions of a CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase. In some embodiments, the one or more regions of the BaTiO.sub.3 phase are in the shape of granules with a particle size of 0.1-1 m and the one or more regions of the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase are in the shape of polygons such as cubes and/or rhombohedrons, e.g., rhombuses with a particle size of 1-4 m. In some embodiments, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase is in the shape of rhombohedrons with a particle size of 1-4 m. In some embodiments, the one or more regions of the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase may be clustered together in a group of 2-25 rhombuses, preferably 5-20 rhombuses, preferably 10-15 rhombuses. In some embodiments, the one or more regions of the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase may be a single rhombus. In some embodiments the one or more regions of the BaTiO.sub.3 phase may be in a layer of the granules with the one or more regions of the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase protruding from the BaTiO.sub.3 phase layer. In some embodiments, the CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase may form together due to the ferromagnetic properties of the material. In some embodiments, the ceramic composite material is biphasic, including a dielectric BaTiO.sub.3 phase and a magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase.

[0087] In some embodiments, the ceramic composite includes barium (Ba) in an amount of 10-30 mol %, preferably 11-29, preferably 12-28, preferably 13-27, preferably 14-26, preferably 15-25, preferably 16-24, preferably 17-23, preferably 18-22, preferably 19-21 mol %; titanium (Ti) is present in an amount of 10-30 mol % percent, preferably 11-29, preferably 12-28, preferably 13-27, preferably 14-26, preferably 15-25, preferably 16-24, preferably 17-23, preferably 18-22, preferably 19-21 mol %; oxygen (O) is present in an amount of 40-60 mol %, preferably 41-59, preferably 42-58, preferably 43-57, preferably 44-56, preferably 45-55, preferably 46-54, preferably 47-53, preferably 48-52, preferably 49-51 mol %; cobalt (Co) is present in an amount of 0.1-3 mol %, preferably 0.2-2.9, preferably 0.3-2.8, preferably 0.4-2.7, preferably 0.5-2.6, preferably 0.6-2.5, preferably 0.7-2.4, preferably 0.8-2.3, preferably 1.0-2.2, preferably 1.1-2.1, preferably 1.2-2, preferably 1.3-1.9, preferably 1.4-1.8, and preferably 1.5-1.7 mol %; iron (Fe) is present in an amount of 0.1-4 mol %, preferably 0.2-3.9, preferably 0.3-3.8, preferably 0.4-3.7, preferably 0.5-3.6, preferably 0.6-3.5, preferably 0.7-3.4, preferably 0.8-3.3, preferably 1.0-3.2, preferably 1.1-3.1, preferably 1.2-3, preferably 1.3-2.9, preferably 1.4-2.8, preferably 1.5-2.7, preferably 1.6-2.6, preferably 1.7-2.5, preferably 1.8-2.4, preferably 1.9-2.3, preferably 2.0-2.2 mol %; and niobium (Nb) is present in an amount of 0.1-2 mol %, preferably 0.2-1.9, preferably 0.3-1.8, preferably 0.4-1.7, preferably 0.5-1.6, preferably 0.6-1.5, preferably 0.7-1.4, 0.8-1.5, preferably 0.9-1.4, preferably 1.0-1.3, preferably 1.1-1.2 mol % based on a total number of mols of the Ba, Ti, O, Co, Fe, and Nb.

[0088] In some embodiments, the ceramic composite has a dielectric constant of 1-20, preferably 2-19, preferably 3-18, preferably 4-17, preferably 5-16, preferably 6-15, preferably 7-14, preferably 8-13, preferably 9-12, preferably 10-11 at a frequency of 1-10.sup.6 Hz.

[0089] In some embodiments, a dielectric loss of 0.1-7, preferably 0.5-6.5, preferably 1.0-6.0, preferably 1.5-5.5, preferably 2-5, preferably 2.5-4.5, preferably 3-4 at a frequency of 1-10.sup.6, according to ASTM D150.

[0090] In some embodiments, the ceramic composite material has a dielectric loss tangent of 0.01-1, preferably 0.05-0.95, preferably 0.1.0-0.90, preferably 0.15-0.85, preferably 0.2-0.8, preferably 0.25-0.75, preferably 0.3-0.7, preferably 0.35-0.65, preferably 0.4-0.6, preferably 0.45-0.55, and preferably 0.4-0.5 at a frequency of 1-10.sup.6, according to ASTM D150.

[0091] The ceramic composite material of the present disclosure may be used to manufacture antennas, radio frequency transmission components, microwave transmission components, high energy density capacitors, high-voltage insulators, and other applications that may benefit from a composite material with a high dielectric constant. In some embodiments, the ceramic composite material can be used in a high frequency device.

EXAMPLES

[0092] The following examples demonstrate a ceramic composite material as described herein. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.

Process of Preparing CoNb.sub.0.02Fe.sub.1.98O.sub.4 Nanoparticles

[0093] Spinel ferrite CoNb.sub.0.02Fe.sub.1.98O.sub.4 nanoparticles were prepared using the hydrothermal method. Stoichiometric quantities of commercially available cobalt(II) nitrate (Co(NO.sub.3).sub.2) and iron (III) nitrate hexahydrate (Fe(NO.sub.3).sub.3.Math.6H.sub.2O) were dissolved in about 60 mL of deionized water under continuous stirring. At the same time, niobium(V) chloride (NbCl.sub.5) was dissolved in concentrated hydrochloric acid under continuous stirring. The two separate solutions were combined and remained under uninterrupted stirring. Then, sodium hydroxide was added to the mixed solution to adjust the pH to 11. After a while, the solution was placed inside a stainless-steel Teflon autoclave and put in an oven at 180 C. for 10 hours. The obtained solution was washed and dried to get powder of CoNb.sub.0.02Fe.sub.1.98O.sub.4 nanoparticles.

Dielectric Phase

[0094] Sol-gel auto-combustion method was employed to produce the BaTiO.sub.3 (BTO) phase by utilizing titanium(IV) isopropoxide Ti[OCH(CH.sub.3).sub.2].sub.4 and barium acetate (Ba(CH.sub.3COO).sub.2 as raw materials, which were purchased from Sigma Aldrich. Appropriate amounts of Ti[OCH(CH.sub.3).sub.2].sub.4 and Ba(CH.sub.3COO).sub.2 were dissolved under continuous stirring and heating (80 C.) in separate beakers, each containing an ethanolic solution. The two solutions were mixed together under uninterrupted stirring and heating. Later, citric acid (C.sub.6H.sub.8O.sub.7) was added to act as a fuel, and the temperature was slightly increased to 120 C. A milky solution was formed after a while, which later transformed to a gel and then self-propagating combusted. The obtained powder was collected, ground in the agate mortar, and finally, calcined at about 1100 C. for 5 hours to obtain the final BTO sample.

Composites

[0095] Diverse (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composite materials with x=0, 2, 5, 10, 20, and 100% were made by utilizing the above-mentioned ferroelectric and ferrite phases using a solid-state reaction route. Polyvinyl alcohol, acting as a binder, was added to the mixed composite powders. The powders were pressed into disk-shaped (diameter 13 mm) samples using a hydraulic press. The pellets were then sintered at 1200 C. for 4 hours.

Characterizations

[0096] The crystal structure and the phase identification of the prepared composites were determined through X-ray diffraction (XRD) patterns by a Rigaku Benchtop Miniflex diffractometer with CuK.sub.a radiation (manufactured by Rigaku Corporation, 3 Chome-9-12 Matsubaracho, Akishima, Tokyo 196-8666, Japan). Rietveld refinement was carried out using the Match 3 program to determine the structural parameters. The morphological and elemental analyses were performed using a field emission scanning electron microscope (SEM; FEI Quanta). Dielectric measurements were analyzed using Novocontrol Technologies (high-resolution Alpha-A frequency analyzer).

[0097] XRD patterns of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0%, 2%, 5% 10%, 20%, and 100%) are depicted in FIG. 1. XRD patterns have been analyzed by Match 3 software. The patterns of x=0% and x=100% compositions displayed well-defined peaks, revealing the creation of single-phase ferroelectric BaTiO.sub.3 perovskite with tetragonal structure (ICDD card no. 96-901-4669) and single-phase CoFe.sub.1.98Nb.sub.0.02O.sub.4 ferrite with cubic spinel structure (ICDD card no. 96-153-5821), respectively. The tetragonal structure observed for pure BTO was confirmed by the splitting (002)/(200) at 2 45. For both cases, the XRD patterns did not show any traces of impurity phases, indicating the high purity of the synthesized BTO and CoNb.sub.0.02Fe.sub.1.98O.sub.4 samples.

[0098] The analysis of different composites (x=2%, 5%, 10%, and 20%) showed that the perovskite and ferrite exist distinctly in the composites. It supported that the BTO phase formed a perovskite structure (space group, P4 mm), while the CoNb.sub.0.02Fe.sub.1.98O.sub.4 ferrite phase formed a spinel structure. The splitting (002)/(200) observed for pure BTO was merged into a single peak (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites. This indicated that a transformation from tetragonal to cubic phase occurred when the CoNb.sub.0.02Fe.sub.1.98O.sub.4 was added to the BTO. Moreover, the absence of any other distinct peak indicated that an intermediate phase is not formed at the interfaces between the constituent phases during the sintering process. It was also observed that the ferrite phase is not detected for low concentrations of CoNb.sub.0.02Fe.sub.1.98O.sub.4. The peak intensity of the ferrite phase increased with the rise in CoNb.sub.0.02Fe.sub.1.98O.sub.4 content. Analysis of CoFe.sub.2O.sub.4-BTO showed no trace of ferrite phase until an 8% of CoFe.sub.2O.sub.4 content was reached. This effect may be attributed to the detection limit of XRD for very low concentrations and the fact that the intensity of the X-rays diffracted from CoFe.sub.2O.sub.4 planes is less than that of BTO.

[0099] The crystallite size (D.sub.XRD) of the synthesized products was determined by Scherrer's equation:

[00001]$\begin{array}{cc}{D}_{\mathrm{XRD}}=\frac{0.9}{\cos }& \left(1\right)\end{array}$

where is the incident X-ray wavelength, is the full width at half maximum (FWHM) of the XRD peak, and is the Bragg's angle. The obtained D.sub.XRD values for both BTO (using 101 peak for the tetragonal phase and 110 peak for the cubic phase) and CoNb.sub.0.02Fe.sub.1.98O.sub.4 (using 311 peak) phases existing in the different composites are plotted in FIG. 2. The crystallite sizes of pure BTO and CoNb.sub.0.02Fe.sub.1.98O.sub.4 have been realized to be 36.8 nm and 10.6 nm, respectively. For the prepared composites, the crystallite size for the BTO phase is gradually decreasing with increasing x content. It decreased from 36.2 nm for x=2% to 27.8 nm for x=20%, whereas the crystallite size for the CoNb.sub.0.02Fe.sub.1.98O.sub.4 phase is increasing with increasing x content. Indeed, some of the magnetic particles will tend to agglomerate because of their magnetic nature, creating practically dense and compacted granules. Under heat treatment, the crystallite size of the CoNb.sub.0.02Fe.sub.1.98O.sub.4 phase will tend to increase with increasing the concentration of the magnetic phase, limiting the growth of the BTO phase [Rather G H, Ikram M. Magnetoelectric coupling in terbium doped particulate multiferroic composites based on BaTiO.sub.3CoFe.sub.2O.sub.4. Physica B. 2020; 599:412577, incorporated herein by reference in its entirety].

[0100] The surface morphology graphs for (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites, where x=0%, 2%, 5%, 10%, and 20%, are taken by means of SEM technique and presented in FIG. 3. These micrographs disclosed how the grains vary with the inclusion of the magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase. The pristine BTO sample (FIG. 3A) contained closely spherical grains with a high density of pores. However, SEM observations of BTO+x % CoNb.sub.0.02Fe.sub.1.98O.sub.4 composites, where x=2%, 5%, 10%, and 20% (FIGS. 3B-3E), indicated the existence of dissimilar particles in terms of shape and size, which belong to CoFe.sub.1.98Nb.sub.0.02O.sub.4 and BTO phases. The distribution of CoFe.sub.1.98Nb.sub.0.02O.sub.4 and BTO phases was confirmed by elemental mappings performed using the EDX system coupled with SEM (FIG. 4). The elemental mappings indicated that some regions are rich with Ba and Ti elements, while some other regions are rich with Co and Fe elements. Accordingly, it has been established that the bright regions observed in FIGS. 3B-3E) largely resemble to the BTO grains, whereas the darkened regions are largely associated with the CoFe.sub.1.98Nb.sub.0.02O.sub.4 spinel ferrite grains. Furthermore, compared to the pure BTO sample, the average BTO grains size is slightly reduced after the inclusion of magnetic spinel ferrite CoFe.sub.1.98Nb.sub.0.02O.sub.4 phase. The magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 grains were found to increase as x % concentration rises, which could be mainly ascribed to their magnetic nature that leads them to agglomerate. It could be also noticed that the density of pores greatly decreased for different composites (i.e., >2%), and very dense and compacted granules are clearly observed for higher x % contents (particularly composites with x=10% and 20%).

[0101] FIGS. 5A and 5B show elemental EDX spectra and the corresponding atomic ratios for pure BTO and composite 90% BTO+10% CoNb.sub.0.02Fe.sub.1.98O.sub.4 sample, respectively. EDX spectrum of pure BTO (FIG. 5A) revealed that Ba, Ti, and O are present, wherein the atomic percentage ratio of Ba to Ti is about 1:1. FIG. 5B confirmed the existence of distinct elements Ti, Ba, Nb, Fe, Co, and O, constituting the BTO+CoNb.sub.0.02Fe.sub.1.98O.sub.4 composite with no existence of any foreign elements. Within this composite, the atomic percentage ratios of Ba:Ti and Co:NbFe are almost 1:1 and 1:2, respectively. For the whole composite system, the atomic percentages of elements belonging to the magnetic phase CoNbFe constitute closely 10% of the elements belonging to the dielectric phase BaTi. It is evident that the atomic ratios closely resemble the calculated cations stoichiometry used for the preparation of different samples. The studies performed by means of SEM and XRD techniques established the ability to successfully create biphasic composites using the solid-state reaction method.

[0102] Dielectric constant () versus applied frequency () for (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composite samples are displayed in FIG. 6. The inset of FIG. 6 shows the variation in with frequency, which revealed a typical polarization behavior of ferroelectric BTO (x=0%). The dielectric constant almost remains unchanged up to =10.sup.4 Hz and decreased exponentially beyond this frequency. A decrease in the dielectric constant at >10.sup.4 Hz for ferroelectric BTO is correlated to the defects' motion and domain walls' vibrations. Low-frequency dielectric polarization is observed for the CoNb.sub.0.02Fe.sub.1.98O.sub.4 sample, which is a typical behavior of ferrite materials. Space charge polarization is a major driving force for observed dielectric polarization in (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composite samples. The observed dielectric behavior can be understood based on the Maxwell-Wagner layer model according to Koop's phenomenological theory. Electronic polarization could maintain with AC electric fields until frequency surpasses its relaxation frequency, whereas the individual polarization ends alternating with the frequency of the electric field, leading to dispersion in . Not all dipoles display the same relaxation frequency resulting in a gradual occurrence of dispersion rather than a sharp decrease.

[0103] Furthermore, the polarization in ferrite-ferroelectric composites is analogous to the conduction mechanism [Rabinkin I T, Novikova Z I. Ferrites, Izv Acad. Nauk USSR Minsk. 1960; 146, incorporated herein by reference in its entirety], and can be obtained by the percentage of electron exchange interaction amongst:

Fe.sup.2+.Math.Fe.sup.3++e.sup.

Co.sup.2+.Math.Co.sup.3++e.sup.

[0104] From FIG. 6, it is noticed that the BTO sample shows the highest 8 values among all investigated samples since the ferroelectric phase is known to possess a higher dielectric constant compared to the ferromagnetic phase.

[0105] FIGS. 7 and 8 illustrate the variations in dielectric loss () and dielectric loss tangent (tan ) with applied frequency for all investigated samples of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4. It is observed that and tan is small for pure BTO sample and BTO+CoNb.sub.0.02Fe.sub.1.98O.sub.4 composites and maximum for pure CoNb.sub.0.02Fe.sub.1.98O.sub.4. This behavior suggests that could increase with the rise in the ferromagnetic CoNb.sub.0.02Fe.sub.1.98O.sub.4 phase. This expectation is correlated to the difference in resistivity of the ferroelectric (BTO) and ferromagnetic (CoNb.sub.0.02Fe.sub.1.98O.sub.4) phase. The relaxation-related peak in and tan plots were observed for some samples and can be understood by Rezlescu model [Rezlescu N, Rezlescu E. Dielectric properties of copper containing ferrites. physica status solidi (a). 1974; 23(2):575, incorporated herein by reference in its entirety]. The condition for the peak in the and tan of these samples is related to:

[00002]$\begin{array}{cc}=1& \left(2\right)\end{array}$

where is the relaxation time and =2.sub.max, which is related to the jumping probability:

[00003]$\begin{array}{cc}=\frac{1}{2p}& \left(3\right)\end{array}$$\begin{array}{cc}\mathrm{or}{f}_{\max }p& \left(4\right)\end{array}$

[0106] Thus, a peak can be obtained as a result of the frequency of charge hopping among cations coinciding with the frequency of the electric field.

[0107] Low values of dielectric loss tangent less than 1 are observed for different composites (x=2, 5, 10, and 20%). More specifically, composite materials with x5% displayed very low values of dielectric loss tangent (below 0.1), along with good stability over the range of frequency. Generally, the increase in tan results from a delay in polarization with an alternating field, which could be caused by the hopping of electrons from Fe.sup.2+ to Fe.sup.3+, the loss in conduction because of poor densification and the presence of defects and impurities. Losses because of conduction appear at low frequencies. Hence, the observed low dielectric losses in x5% compositions could be ascribed to the homogeneous structure, the good stoichiometry, and the contribution of the ferrite phase. This is evidenced by the above-reported SEM observations. The obtained results indicated that the present composite products might be suitable for high-frequency device applications like antennas, filters, dielectric resonators, and others.

[0108] The imaginary part of impedance (Z) was plotted versus the real part of impedance (Z) in FIG. 9, known as Nyquist or Cole-Cole plot. It is known that two semi-circles can be observed in the Cole-Cole plots. The first semi-circle, as a result of resistance originating from the grain boundary (R.sub.gb) can appear at a lower frequency; and the second semicircle, due to resistance of grain (R.sub.g) can appear at a higher frequency. A close observation of FIG. 9A revealed that no semicircle was observed at a lower frequency, and probably no contribution of resistance is offered by the grain boundaries towards dielectric properties. An expanded view of Cole-Cole plot, shown in FIG. 9B, reveals a depressed type of semi-circle observed at a higher frequency. Thus, grain contributed higher resistance in the dielectric behavior of the prepared samples. The electrical modulus plane plots of different samples are presented in FIG. 10, where the imaginary M is plotted versus the real part M of modulus. The capacitance value can be obtained using these plots with a contribution from the grain boundary and grain. Only one semicircle is observed for the pure BTO (x=0%) and 98% BTO+2% CoNb.sub.0.02Fe.sub.1.98O.sub.4 samples; for x>2%, a second semi-circle also starts to form. Two semicircles in the modulus plane plots suggest two relaxation processes occur. It can be concluded from FIGS. 9 and 10 that resistance of the materials increased with the increase in the ferromagnetic CoNb.sub.0.02Fe.sub.1.98O.sub.4 phase, and thus resulted in lower dielectric properties compared to pure BTO.

[0109] To this end, composite materials of (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites (x=0, 2, 5, 10, 20, and 100%) were developed using the solid-state reaction. XRD, SEM, and EDX analyses showed that the perovskite BTO and spinel ferrite phases distinctly exist in the composites. No traces of any impurity are noticed. A transformation from the tetragonal BTO phase in pristine x=0% sample to the cubic BTO phase occurred when the CoNb.sub.0.02Fe.sub.1.98O.sub.4 was added to the BTO phase. The addition of the CoNb.sub.0.02Fe.sub.1.98O.sub.4 phase into the BTO phase resulted in an increase in the lattice parameters and cell volume of the prepared composites. Compared to the x=0% sample, the average BTO grains size is slightly reduced after the inclusion of magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 spinel ferrite phase, while magnetic CoFe.sub.1.98Nb.sub.0.02O.sub.4 grains are enlarged as x % concentration rises. The dielectric properties are also investigated at room temperature in a frequency range of 1 to 10.sup.6 Hz. The dielectric loss tangent indicated low values lesser than 1 for different (100-x) % BTO+x % CoFe.sub.1.98Nb.sub.0.02O.sub.4 composites with x=2, 5, 10, and 20%. Among these composites, the sample prepared with x content higher than 5% displayed very low dielectric loss tangent (below 0.1) along with good stability over the frequency range of 1 to 10.sup.6 Hz. This is mainly ascribed to the homogeneous structure, the stoichiometry, and the contribution of the ferrite phase. The current results indicated that the present composite materials might be suitable for high-frequency device applications.

[0110] Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein.