Zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitor

Abstract

The invention belongs to the technical field of electronic materials, and particularly relates to a zinc niobate-based composite ceramic material for an MLCC microwave ceramic capacitor. According to the invention, a microwave dielectric ceramic composite material containing a niobate component is used as a main material, and Ti and W are used for jointly replacing B-site Nb ions in ZnNb2O6 to form a ZnNb1.98 (TiW) 0.01 O6 microwave ceramic main phase; a Ni0. 5Ti0. 5NbO4 material with tau f = + 78.6 ppm / DEG C and epsilon r = 56.3 is selected as a composite phase, and the composite ceramic material is obtained by sintering at 1050-1150 DEG C through a traditional solid-phase reaction method, so that near-zero regulation and control of a temperature coefficient of resonance frequency of the material, a medium dielectric constant and a high Q value are realized while no impure phase is generated in a two-phase compounding process. The method can be applied to ceramic capacitor manufacturing based on the multi-layer ceramic co-firing technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and particularly relates to a zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors. The main material is a microwave dielectric ceramic composite material with a niobate composition, which has characteristics such as adjustable temperature coefficient of resonant frequency, high Q, and medium permittivity, and can be applied to microwave ceramic capacitors based on the multi-layer ceramic co-firing technology and the like. Background Art

[0002] Multi-layer ceramic capacitors (MLCCs) are a type of typical passive components and are widely used in fields such as consumer electronics, automotive electronics, high-frequency communication equipment, and industrial control. In particular, under high-frequency usage conditions, more attention needs to be paid to the reliability of MLCCs, especially to ensure the frequency stability of MLCCs under extreme conditions.

[0003] To meet the above requirements, the preparation of microwave dielectric ceramic materials with a near-zero temperature coefficient of resonant frequency (τ f ), a high Q×f value, and a medium dielectric constant (ε r ) has become the key to ensuring the stable operation of MLCCs under extreme conditions. Among them, ZnNb 2 O 6 as a microwave dielectric ceramic material with a relatively high Q×f value (76000 GHz) has received wide attention. However, its temperature coefficient of resonant frequency is relatively low (-76 ppm / °C), which will significantly affect the frequency stability performance when the temperature changes greatly, severely limiting its application. To improve this defect, researchers usually compound the corresponding microwave dielectric ceramic materials with positive high-temperature coefficient of resonant frequency ceramic materials (typically TiO 2 , CaTiO 3 , etc.) to offset the influence of temperature changes on the operation of the device. According to the effective medium theory, a large amount of compounding is often required, and at the same time, impurity phases may be introduced, thus severely deteriorating the dielectric properties of the material and affecting its sintering properties. For example, Guo M, Li Y, Dou G, et al. (Low-temperature sintered ZnNb 2 O 6 -CaTiO 3 ceramics with near-zero τf. Materials Chemistry and Physics 2014, 147: 728-34.) improved its temperature coefficient of resonant frequency by adding CaTiO 3 , etc., but the Q×f value decreased sharply (τ f = 0, Q×f = 10000 GHz).

[0004] Therefore, it is necessary to find a more suitable method to improve the temperature coefficient of resonance frequency of zinc niobate ceramics and take into account the microwave dielectric properties of zinc niobate ceramics to meet the application of this ceramic material in MLCC. Summary of the Invention

[0005] In view of the above problems, in order to compensate the temperature coefficient of resonance frequency of zinc niobate-based ceramic materials and take into account their microwave dielectric and sintering properties, the present invention provides a zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors; the present invention uses Ti and W to jointly replace the B-site Nb ions in ZnNb 2 O 6 to form a ZnNb 1.98 (TiW) 0.01 O 6 microwave ceramic main phase, select τ f = +78.6 ppm / °C, ε r = 56.3 of Ni 0.5 Ti 0.5 NbO 4 material as the composite phase, and sinter the composite ceramic material at 1050°C to 1150°C by the traditional solid-phase reaction method. While ensuring that no impurity phase is generated during the two-phase composite process, the temperature coefficient of resonance frequency of the material can be adjusted to be nearly zero and the characteristic of high Q value can be maintained.

[0006] A preparation method of a zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors includes the following steps:

[0007] Step 1: Weigh the raw materials ZnNb 2 O 6 , TiO 2 and WO 3 and prepare them according to the molar ratio of ZnNb 1.98 (TiW) 0.01 O 6 for standby.

[0008] Step 2: Ball-mill and mix the raw materials prepared in Step 1, and then pass through a 40-60 mesh sieve.

[0009] Step 3: Pre-sinter the ball-milled powder obtained in Step 2 at 950°C to 1050°C for 4 h to 6 h with a heating rate of 1°C / min to 2°C / min to obtain the main base material ZnNb 1.98 (TiW) 0.01 O 6 powder.

[0010] Step 4: Mix the ZnNb 1.98 (TiW) 0.01 O 6 powder and Ni 0.5Ti 0.5 NbO 4 Ingredients, 0.5 ≤ x ≤ 0.7, ball mill and mix evenly, and sieve through a 40 - 60 mesh sieve.

[0011] Step 5: Add an aqueous PVA solution as a binder to the powder after mixing in Step 4 for granulation, and then press it into a shape.

[0012] Step 6: Sinter the sample pressed into a shape in Step 6 at 1050 °C - 1150 °C, with a heating rate of 1 °C / min - 2 °C / min and a holding time of 4 h - 6 h; let it cool naturally to obtain the zinc niobate - based composite ceramic material for MLCC microwave ceramic capacitors.

[0013] Furthermore, the ball - milling and mixing process is as follows: the rotational speed of the ball mill is 250 r / min - 300 r / min, ball - mill for 8 h - 12 h, and then dry at 80 °C - 120 °C.

[0014] Furthermore, in Step 5, the concentration of the aqueous PVA solution is 8 - 12 wt%.

[0015] Furthermore, in Step 5, the pressing into a shape is carried out under a pressure of 18 MPa - 20 MPa for 2 min - 3 min.

[0016] Furthermore, the zinc niobate - based composite ceramic material prepared by the above - mentioned method is used for ceramic capacitors based on the multi - layer ceramic co - firing technology.

[0017] To sum up, the present invention uses a microwave dielectric ceramic composite material with a niobate component as the main material, and uses Ti and W to jointly replace the B - site Nb ions in ZnNb 2 O 6 to form the main phase of the ZnNb 1.98 (TiW) 0.01 O 6 microwave ceramic; Select the Ni f with τ r = +78.6 ppm / °C and ε 0.5 = 56.3 0.5 Ti 4 NbO Description of the Drawings

[0018] Figure 1 is the process flow chart of the present invention.

[0019] Figure 2 XRD patterns of the ceramic materials in Examples 1-5.

[0020] Figure 3 For the τ of the ceramic materials in Examples 1-5 f value.

[0021] Figure 4 For the Q×f values of the ceramic materials in Examples 1-5

[0022] Figure 5 For the dielectric constant values of the ceramic materials in Examples 1-5 Detailed implementation mode

[0023] The present invention will be further described in detail below with reference to the drawings and examples.

[0024] Example:

[0025] A zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors, with an adjustable resonance frequency temperature coefficient. The specific preparation method is as Figure 1 shown, and includes the following steps:

[0026] Prepare the main base material ZnNb 1.98 (TiW) 0.01 O 6 powder:

[0027] Step 1. Weigh the raw materials of ZnNb 2 O 6 :TiO 2 :WO 3 according to the molar ratio of ZnNb 1.98 (TiW) 0.01 O 6 for standby.

[0028] Step 2. Ball-mill the raw materials prepared in Step 1 according to the mass ratio of material: deionized water: balls of 1:1:1.5. The rotation speed of the ball mill is 300 r / min, and the ball-milling time is 12 h for ball-milling and mixing; then dry at 100 °C and pass through a 40-mesh sieve.

[0029] Step 3. Pre-sinter the ball-milled powder obtained in Step 2 at 1000 °C for 4 h with a heating rate of 2 °C / min to obtain the main base material ZnNb 1.98 (TiW) 0.01 O 6 powder.

[0030] Step 4. Mix the ZnNb 1.98 (TiW) 0.01 O 6 powder with Ni 0.5 Ti 0.5 NbO4 Mix them in the proportions of x = 0.2, x = 0.5, x = 0.6, x = 0.7, and x = 0.8 respectively, corresponding to Examples 1 to 5 respectively.

[0031] Step 5: Add an aqueous PVA solution (concentration: 12 wt%) as a binder to the powder mixture obtained in Step 4 for granulation, and press it into a shape at 20 MPa with a pressure holding time of 2 min.

[0032] Step 6: Sinter the sample pressed into a shape in Step 5 at 1100 °C with a heating rate of 2 °C / min and a heat preservation time of 6 h; wait for it to cool naturally to obtain the zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors.

[0033] Figure 2 XRD patterns of the ceramic materials obtained in Examples 1 - 5, where x refers to the main base material ZnNb 1.98 (TiW) 0.01 O 6 Powder and Ni 0.5 Ti 0.5 NbO 4 The corresponding molar ratio.

[0034] Figure 3 For the τ f Values of the ceramic materials in Examples 1 - 5, where Mole ratio refers to Ni 0.5 Ti 0.5 NbO 4 The corresponding molar ratio x. The τ f Value increases with the increase of the molar ratio within the range of -100 to +75, indicating that arbitrary regulation of the resonance frequency temperature coefficient within this range is achieved. Particularly, when x = 0.5 and x = 0.7, the resonance frequency temperature coefficient is nearly zero, and when x = 0.6, the resonance frequency temperature coefficient is zero. This shows that by changing the content of Ni 0.5 Ti 0.5 NbO 4 The temperature drift characteristics of the ceramic can be precisely adjusted to meet the requirements of different microwave devices for temperature stability.

[0035] Figure 4 For the Q×f values of the ceramic materials in Examples 1 - 5, where Mole ratio refers to Ni 0.5 Ti 0.5 NbO 4 The corresponding molar ratio x.

[0036] Figure 5 For the dielectric constant values of the ceramic materials in Examples 1 - 5, it can be seen that they increase with the increase of Mole ratio and all remain within the medium range.

[0037] From the test analysis results of the above embodiments, the various properties of zinc niobate ceramic materials with different x ratios can be seen. According to the results, when x < 0.5 or x > 0.8, the temperature coefficient of resonance frequency of the material does not meet the condition of near zero, and when x > 0.8, the Q×f value drops too severely. When 0.5 ≤ x ≤ 0.7, the zinc niobate-based ceramic material realizes near-zero regulation of the temperature coefficient of resonance frequency in the range of -25 to +30. When x = 0.6, the temperature coefficient of resonance frequency τ f value is zero, the dielectric constant is 32, and the Q×f value is 30000 GHz.

[0038] It is proved that the present invention is based on zinc niobate ceramic materials with high Q×f values, and by using Ti and W to jointly replace ZnNb 2 O 6 in the B-site Nb ions to further increase the Q×f value, and then compound with Ni 0.5 Ti 0.5 NbO 4 to provide a microwave ceramic capacitor with characteristics such as near-zero regulation of the temperature coefficient of resonance frequency, medium, and high Q×f value, which can be used in multi-layer ceramic co-firing technology.

Claims

1. A method for preparing a zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors, characterized in that: The following steps are involved: Step 1: Mix the raw materials ZnNb2O6, TiO2 and WO3 according to ZnNb 1.98 (TiW) 0.01 The ingredients are prepared in a molar ratio of 0.06 for later use; Step 2, after ball milling and mixing the raw materials prepared in step 1, pass through a 40-60 mesh sieve; Step 3: pre-sinter the ball-milled powder obtained in step 2 at 950°C to 1050°C for 4h to 6h at a heating rate of 1°C / min to 2°C / min to obtain the main base material ZnNb 1.98 (TiW) 0.01 O6 powder; Step 4: ZnNb in a molar ratio of 1-x:x 1.98 (TiW) 0.01 O6 powder and Ni 0.5 Ti 0.5 NbO4 ingredients, 0.5≤x≤0.7, ball mill and mix through 40-60 mesh screen; Step 5, adding PVA aqueous solution as a binder to the powder mixed in step 4 to granulate, and then pressing and molding; Step 6: Sinter the sample pressed in step 6 at 1050°C to 1150°C, with a heating rate of 1°C / min to 2°C / min and a holding time of 4h to 6h; and wait for it to cool naturally to obtain a zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors.

2. The method for preparing the zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors according to claim 1, characterized in that: The ball milling and mixing process is as follows: the ball mill speed is 250 r / min to 300 r / min, the ball milling is performed for 8 h to 12 h, and then the ball milling is performed at 80° C. to 120° C.

3. The method for preparing the zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors according to claim 1, characterized in that: The concentration of the PVA aqueous solution in step 5 is 8-12 wt %.

4. The method for preparing the zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors according to claim 1, characterized in that: The compression molding in step 5 is carried out by maintaining the pressure at 18 MPa to 20 MPa for 2 minutes to 3 minutes.

5. A zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors, characterized in that: Prepared by the method according to any one of claims 1 to 4.

6. The zinc niobate-based composite ceramic material for MLCC microwave ceramic capacitors as claimed in claim 5, characterized in that: Used in ceramic capacitors based on multilayer ceramic co-firing technology.

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