MICROWAVE DIELECTRIC CERAMIC MATERIAL AND PREPARATION METHOD THEREOF

Abstract

A temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material and a preparation method thereof are provided. Using ion doping modification to form solid solution structure is an important measure to adjust microwave dielectric properties, especially the temperature stability. Based on formation rules of the solid solution, ion replacement methods are designed including Ni.sup.2+ ions are replaced by Cu.sup.2+ ions, and (Ni.sub.1/3Ta.sub.2/3).sup.4+ composite ions are replaced by [(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sup.4+ composite ions, which considers that cations with similar ionic radii to Ni.sup.2+ and Ta.sup.5+ ions can be introduced into the NiTa.sub.2O.sub.6 ceramic for doping under the same coordination environment (coordination number=6), and therefore a ceramic material with the NiTa.sub.2O.sub.6 solid solution structure can be obtained. The microwave dielectric ceramic material with excellent temperature stability and low loss is finally prepared by adjusting molar contents of each of doped ions, and its microwave dielectric properties are excellent.

Claims

1. A temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material, wherein a general chemical formula of the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material is expressed as [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2, where 0.02≤x≤0.08, 0.05≤y≤0.2, 0.02≤z≤0.06; the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material is prepared by a solid-state method; under a condition of 0.02≤x≤0.08, 0.05≤y≤0.02, and 0.02≤z≤0.06, the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material has a single phase of NiTa.sub.2O.sub.6 solid solution and has a crystal structure of the NiTa.sub.2O.sub.6 solid solution; and wherein a sintering temperature of the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material is in a range of 1325° C. to 1400° C., a relative dielectric constant ε.sub.r is in a range of 19 to 23, a product of a quality factor Q and a resonant frequency f is in a range of 30000 gigahertz (GHz) to 52000 GHz, and a temperature coefficient of resonant frequency τ.sub.f is in a range of −5 parts per million for per Celsius degree (ppm/° C.) to 5 ppm/° C.

2. The temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material according to claim 1, wherein when x=0.05, y=0.15, z=0.02, and the sintering temperature of the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material is 1375° C., the relative dielectric constant ε.sub.r is 20.91, a dielectric loss is 2.14×10.sup.−4, the product of the quality factor Q and the resonant frequency f is 50028 GHz, and the temperature coefficient of resonant frequency τ.sub.f is −1.7 ppm/° C.

3. A preparation method for a temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material, comprising: step 1: mixing raw powders of nickel monoxide (NiO), cupric oxide (CuO), aluminum oxide (Al.sub.2O.sub.3), niobium pentoxide (Nb.sub.2O.sub.5), stannic oxide (SnO.sub.2), and tantalum pentoxide (Ta.sub.2O.sub.5) according to a general chemical formula expressed as [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2, where 0.02≤x≤0.08, 0.05≤y≤0.2, 0.02≤z≤0.06; step 2: putting the mixed raw powders prepared in the step 1 into a ball milling tank, milling media being zirconium balls and deionized water, and performing ball milling according to a mass ratio of the mixed raw powders:the zirconium balls:the deionized water of 1:6˜8:4˜6 for a duration in a range of 6 hours˜8 hours to obtain a first milled material; taking out the first milled material and drying the first milled material in an oven at a temperature in a range of 80° C.˜120° C. to obtain a first dried material; sieving the first dried material with a mesh screen with a mesh sieve size in a range of 40˜60 mesh; then pre-sintering the sieved material in an atmosphere at a temperature in a range of 1000° C.˜1100° C. for a duration in a range of 3 hours˜5 hours; step 3: performing ball milling according to a mass ratio of the pre-sintered material:zirconium balls:deionized water of 1:5˜7:1˜3 for a duration in a range of 3 hours˜6 hours to obtain a second milled material; taking out the second milled material and drying the second milled material to obtain a second dried material; then adding a polyvinyl alcohol solution into the second dried material for granulation, thereby obtaining a granulated material; and step 4: pressing and molding the granulated material prepared in the step 3 to obtain a molded material, performing a debinding process on the molded material at a temperature in a range of 600° C.˜650° C., and sintering the molded material after the debinding process in an atmosphere at a temperature in a range of 1325° C.˜1400° C. for a duration in a range of 4 hours˜6 hours; thereby obtaining a [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2 microwave dielectric ceramic material as the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 shows X-ray diffraction (XRD) patterns of ceramic samples corresponding to embodiments 7, 8, and 9.

[0016] FIG. 2 shows a morphology diagram of the ceramic sample corresponding to the embodiment 7 under a scanning electron microscope (SEM).

DETAILED DESCRIPTION OF EMBODIMENTS

[0017] The disclosure is further described in detail below in combination with attached drawings and embodiments.

[0018] Step 1, raw powders of NiO, CuO, Al.sub.2O.sub.3, Nb.sub.2O.sub.5, SnO.sub.2, and Ta.sub.2O.sub.5 are mixed with mole ratios according to a general chemical formula expressed as [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2, where x=0.05, y=0.15, z=0.02, 0.04, 0.06.

[0019] Step 2, the mixed raw powders prepared in the step 1 are put into a ball milling tank, milling media are zirconium balls and deionized water, and first planetary ball milling is performed according to a mass ratio of the mixed raw powders:the zirconium balls:the deionized water of 1:6:4 for 6 hours to obtain a first milled material. The first milled material is taken out and the first milled material is dried in an oven at a temperature of 100° C. to obtain a first dried material. The dried material is sieved by a 60-mesh screen, and then the sieved material is pre-sintered in an atmosphere at a temperature of 1100° C. for 3 hours.

[0020] Step 3, the pre-sintered material is added into the ball milling tank to perform second planetary ball milling according to a mass ratio of the pre-sintered material:the zirconium balls:the deionized water of 1:6:3 for 4 hours to obtain a second milled material. The second milled material is taken out and the second milled material is dried to obtain a second dried material. Then, a polyvinyl alcohol solution is added into the second dried material for granulation, thereby a granulated material is obtained.

[0021] Step 4, the granulated material obtained in the step 3 is put into a mould with a diameter of 12 mm (Φ12), and a molded material is formed by dry-pressing under pressure of 20 megapascals (MPa). Therefore, a cylindrical block with a size of 12 mm×6 mm can be obtained. Then, the cylindrical block is kept at a temperature of 650° C. for 2 hours to remove ceramic binders (also referred to a debinding process), then the temperature is raised to 1325° C.˜1400° C. and the temperature is kept for 4 hours to finally obtain a microwave dielectric ceramic material having the general chemical formula expressed as [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2 (also referred to the modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material with stable temperature).

[0022] 12 ceramic samples corresponding to 12 embodiments are made according to the above steps. FIG. 1 shows XRD patterns of ceramic samples corresponding to embodiments 7, 8, and 9. It can be found that phase compositions of the ceramic samples of the three different embodiments correspond to Joint Committee Powder Diffraction Standards (JCPDS) card No. 32-0702 which is a standard card of NiTa.sub.2O.sub.6 by retrieval. Doping ions are solid dissolved to the cationic lattices and no diffraction peak of second phase is found, which indicates that the [(Ni.sub.1-xCu.sub.x).sub.1/3Ta.sub.2/3].sub.1-z[(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sub.zO.sub.2 ceramic belongs to the solid solution of NiTa.sub.2O.sub.6 structure.

[0023] FIG. 2 shows a morphology diagram microscope of SEM corresponding to embodiment 7; it can be seen that the crystalline grain growth of the ceramic sample of the embodiment 7 is sufficient, and the grain boundaries are clearly visible, indicating that there is no over-burning phenomenon, but there are still some micro-pores in the ceramic sample.

[0024] Specific components and microwave dielectric properties of the ceramic samples in various embodiments (i.e., the following 12 embodiments) are as follows.

TABLE-US-00001 TABLE 1 Specific components of ceramic samples in various embodiments Number Sintering of temper- embodi- Mass of each component/g ature ments NiO CuO Ta.sub.2O.sub.5 Al.sub.2O.sub.3 Nb.sub.2O.sub.5 SnO.sub.2 (° C.) 1 13.487 0.756 83.990 0.044 0.232 1.491 1325 2 13.243 0.742 82.472 0.089 0.465 2.989 3 12.998 0.729 80.946 0.134 0.699 4.493 4 13.487 0.756 83.990 0.044 0.232 1.491 1350 5 13.243 0.742 82.472 0.089 0.465 2.989 6 12.998 0.729 80.946 0.134 0.699 4.493 7 13.487 0.756 83.990 0.044 0.232 1.491 1375 8 13.243 0.742 82.472 0.089 0.465 2.989 9 12.998 0.729 80.946 0.134 0.699 4.493 10 13.487 0.756 83.990 0.044 0.232 1.491 1400 11 13.243 0.742 82.472 0.089 0.465 2.989 12 12.998 0.729 80.946 0.134 0.699 4.493

TABLE-US-00002 TABLE 2 Microwave dielectric properties of ceramic samples in various embodiments Relative External Thick- dielectric τ.sub.f Number of diameter ness constant Tanδ Q × f (ppm/ embodiments (mm) (mm) ∈.sub.r (10.sup.−4) (GHz) ° C.) 1 10.89 3.89 19.41 2.87 36879 −3.1 2 10.42 4.35 21.62 2.81 34100 −2.2 3 10.43 4.57 21.45 2.88 32673 −0.9 4 10.76 4.3 20.53 2.52 40225 −1.4 5 10.44 4.39 22.01 2.71 35230 −1.8 6 10.44 4.48 21.43 2.8 33623 1.2 7 10.61 3.65 20.91 2.14 50028 −1.7 8 10.44 4.48 21.42 2.62 36264 −1.2 9 10.47 4.55 21.03 2.6 36356 1 10 10.63 4.16 20.74 2.34 42828 −0.8 11 10.43 4.49 21.89 2.83 33065 −1.3 12 10.5 4.57 20.42 2.84 33600 1.7

[0025] According to the data provided in TABLE 1 and TABLE 2, when x=0.05, y=0.15 and z=0.02, 0.04, 0.06; the sintering temperature is in a range of 1325° C.˜1400° C., and the temperature coefficient of resonant frequency τ.sub.f is in a range −5 ppm/° C. to 5 ppm/° C., which indicates that these microwave dielectric properties are excellent. In particular, when z=0.02 and a corresponding sintering temperature is 1375° C., (i.e., embodiment 7), the microwave dielectric properties of the ceramic sample (i.e., the temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material) are the best: ε.sub.r=20.91, tan δ=2.14×10.sup.−4, Q×f=50028 GHz, τ.sub.f=−1.7 ppm/° C., which can be widely used in electronic components of high-frequency communication.