MODIFIED NI-TI-TA DIELECTRIC MATERIAL FOR MULTI-LAYER CERAMIC CAPACITOR AND LOW-TEMPERATURE PREPARATION METHOD THEREOF

Abstract

A modified Ni—Ti—Ta dielectric material for multi-layer ceramic capacitor (MLCC) and a low-temperature preparation method thereof are provided. By using characteristics that radii of the Cu.sup.2+ ion and (Al.sub.½Nb.sub.½).sup.4+ ion are close to those of Ni and Ti elements, respectively, Cu.sup.2+, Al.sup.3+ and Nb.sup.5+ ions are introduced into a Ni.sub.0..sub.5Ti.sub.0.5TaO.sub.4 matrix for partial substitution, a negative temperature coefficient of dielectric constant of -220±30 ppm/°C is provided while a sintering temperature is significantly reduced, and deterioration factors of loss caused by sintering aids is reduced, so that the dielectric material applied to radio frequency MLCC with low loss, low cost and good process stability is prepared.

Claims

1. A modified nickel-titanium-tantalum (Ni—Ti—Ta) dielectric material for multi-layer ceramic capacitor, wherein a chemical formula of the modified Ni—Ti—Ta dielectric material is as follows: [Cu.sub.0.1Ni.sub.0.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08].sub.0.5TaO.sub.4, and a sintering temperature of the modified Ni—Ti—Ta dielectric material is in a range of 1050° C. to 1150° C.; a crystal structure of the modified Ni—Ti—Ta dielectric material belongs to a Ni.sub.0.5Ti.sub.0..sub.5TaO.sub.4 phase solid solution structure, a dielectric constant of the modified Ni—Ti—Ta dielectric material is in a range of 34 to 40, and a dielectric loss of the modified Ni—Ti—Ta dielectric material is in a range of 2.8×10.sup.-4 to 3.3×10.sup.-4, a quality factor Q × f value of the modified Ni—Ti—Ta dielectric material is in a range of 22000 GHz to 25000 GHz, and a temperature coefficient of dielectric constant is stable and meets R2G temperature characteristics.

2. The modified Ni—Ti—Ta dielectric material for multi-layer ceramic capacitor according to claim 1, wherein when the sintering temperature is 1150° C., the dielectric constant is 39.8, the dielectric loss is 2.8×10.sup.-4, the quality factor Q x f value is 24308 GHz, and the temperature coefficient of dielectric constant is stable and meets R2G temperature characteristics.

3. A method for preparing the modified Ni—Ti—Ta dielectric material for multi-layer ceramic capacitor according to claim 1, comprising: step 1, mixing raw powders of cupric oxide (CuO), nickel oxide (NiO), TiO.sub.2, Al.sub.2O.sub.3, Nb.sub.2O.sub.5 and Ta.sub.2O.sub.5 according to the chemical formula [Cu.sub.0.1NI.sub.0.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08].sub.0.5TaO.sub.4 to obtain a mixed powder; step 2, putting the mixed powder prepared in step 1 into a ball milling tank, performing planet ball milling for 4 ~ 6 hours according to a mass ratio of the mixed powder: zirconium balls: deionized water of 1: 4-6: 5-7 to obtain a mixed slurry, drying the mixed slurry in an oven after the ball milling and then sieving with a 40-200 mesh sieve to obtain a sieved powder; and sintering the sieved powder in an atmosphere of 900-1100° C. for 3 ~ 5 hours to obtain a sintered powder; step 3, performing planet ball milling on the sintered powder obtained in step 2 for 4 ~ 6 hours according to a mass ratio of the sintered powder: zirconium balls: deionized water of 1: 4-6: 3-5 to obtain a ball-milled material, and adding a polyvinyl alcohol solution into the ball-milled material after drying the ball-milled material as a binder to perform granulation to obtain a ceramic raw material; and step 4, performing press-molding on the ceramic raw material prepared in step 3, heating at a heating rate of 2 ~ 5° C./min and discharging glue at 600 ~ 650° C. for 3 ~ 5 hours, and then heating at the same heating rate to a temperature of 1050 ~ 1150° C. and keeping the temperature for 4 ~ 6 hours, thereby obtaining a modified [Cu.sub.0.1Ni.sub.0.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08].sub.0.5TaO.sub.4 dielectric ceramic material.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 illustrates a schematic diagram of an X-ray diffraction (XRD) pattern according to an embodiment 3 of the disclosure.

[0016] FIG. 2 illustrates a schematic diagram of scanning electron microscope (SEM) according to the embodiment 3 of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0017] The disclosure will be further described in detail with the attached drawings and embodiments.

[0018] A method for preparing a modified Ni—Ti—Ta dielectric material for multi-layer ceramic capacitor is provided and includes the following steps.

[0019] Step 1, mixing raw powders of CuO, NiO, TiO.sub.2, Al.sub.2O.sub.3, Nb.sub.2O.sub.5 and Ta.sub.2O.sub.5 according to the chemical formula of [Cu.sub.0.1Ni.sub.0.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08]0.5TaO.sub.4 to obtain a mixed powder.

[0020] Step 2, putting the mixed powder prepared in step 1 into a ball milling tank, performing planet ball milling for 6 hours according to a mass ratio of the mixed powder: zirconium balls: deionized water of 1: 6: 5 to obtain a mixed slurry, drying the mixed slurry in an oven after the ball milling and then sieving with a 200 mesh sieve to obtain a sieved powder; and sintering the sieved powder in an atmosphere of 1000° C. for 5 hours to obtain a sintered powder.

[0021] Step 3, performing planet ball milling on the sintered powder obtained in step 2 for 6 hours according to a mass ratio of the sintered powder: zirconium balls: deionized water of 1: 6: 3 to obtain a ball-milled material, and adding an 8% polyvinyl alcohol solution into the ball-milled material after drying the ball-milled material as a binder to perform granulation to obtain a ceramic raw material.

[0022] Step 4, performing press-molding on the ceramic raw material prepared in step 3, then heating at a heating rate of 5° C./min and discharging glue at 650° C. for 4 hours, and then heating at the same heating rate to a temperature of 1050 ~ 1150° C. and keeping the temperature for 6 hours, thereby obtaining a modified [Cu.sub.0.1Ni.sub.0.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08].sub.0.5TaO.sub.4 dielectric ceramic material.

[0023] In order to better illustrate the effect of the disclosure, three embodiment samples are made according to the above steps. FIG. 1 is the XRD pattern of Embodiment 3. After searching, the phase composition of the ceramic corresponds to the standard card of Ni.sub.0.5Ti.sub.0.5TaO.sub.4, i.e. joint committee on powder diffraction standards (JCPDS) card with No.32-0702, no second phase diffraction peak is found in the system at this time, which indicates that ion substitution will not change the crystal structure at this doping amount, and this type of ceramic belongs to the Ni.sub.0.5Ti.sub.0.5TaO.sub.4 structure.

[0024] FIG. 2 is a SEM topography diagram of Embodiment 3. At this sintering temperature, the grain growth is sufficient, the grain size is small, and there are fewer pores in the microstructure.

[0025] The composition and microwave dielectric properties of the embodiments are shown in Table 1 and Table 2 as follows.

TABLE-US-00001 shows the components of each embodiment sample Embodiment number 1 2 3 Mass of each component CuO 1.330 1.330 1.330 NiO 11.243 11.243 11.243 TiO.sub.2 12.289 12.289 12.289 Al.sub.2O.sub.3 0.341 0.341 0.341 Nb.sub.2O.sub.5 0.889 0.889 0.889 Ta.sub.2O.sub.5 73.907 73.907 73.907 Sintering temperature (°C) 1050 1100 1150

TABLE-US-00002 shows the dielectric properties of each embodiment sample Embodiment number dielectric constant ε.sub.r Tanδ (10.sup.-4) Q*f (GH.sub.z) τ.sub.ε (ppm/°C) -55° C. 85° C. 1 34.8 3.3 22041 -171 -179 2 38.1 3.0 22532 -178 -185 3 39.8 2.8 24308 -196 -202

[0026] From the data shown in Table 1 and Table 2, it can be seen that in Embodiment 3, when the sintering temperature is 1150° C., the dielectric constant and Q×f value of the modified [Cu.sub.0.1Ni.sub.0..sub.9].sub.0.5[Ti.sub.0.92(Al.sub.½Nb.sub.½).sub.0.08].sub.0.5TaO.sub.4 dielectric ceramic material get the best values: ε.sub.r = 39.8, Tan δ = 2.8× 10.sup.-4, Q×f = 24308 GHz, and τ.sub.ε is in the range of -202 ppm/°C to -196 ppm/°C. Compared with literature reports in the related art, the sintering temperature is greatly reduced and the dielectric loss is kept low, at the same time, the temperature coefficient of dielectric constant is relatively stable in the range of -55° C. to 85° C., the modified dielectric ceramic material is suitable for industrial application.