CN1793034A - Chemical preparation process for high dielectric porcelain material - Google Patents

Abstract

The present invention relates to a chemical preparation method of high dielectric ceramic materials, using analytically pure Ta ₂ O ₅ , Nb ₂ O ₅ , AgNO ₃ , NaNO ₃ as raw materials, according to (Ag _x Na _1-x ) [ _Nby Ta _{1 -y} ]O ₃ composition Weigh Ta ₂ O ₅ and Nb ₂ O ₅ according to a specific ratio, add hydrofluoric acid and nitric acid, heat and dissolve in a water bath, weigh AgNO ₃ and NaNO ₃ in proportion, add analytically pure citric acid to obtain lemon acid solution, mix and stir the two solutions, and bake under infrared light to obtain the precursor of (Ag _x Na _1-x )[ _Nby Ta _1-y ]O ₃ , after ball milling and high-temperature calcination, the required of nanopowders. Compared with the solid-phase synthesis method, the liquid-phase synthesis method of the present invention can obviously reduce the loss of the system, make the dielectric constant of the system higher and the absolute value of the temperature coefficient of capacitance smaller.

Description

Chemical Preparation Method of High Dielectric Porcelain Material

Technical field

The invention relates to a chemical preparation method of ceramic material, in particular to a chemical preparation method of high dielectric constant ceramic material.

Background technique

At present, there are many methods for preparing inorganic non-metallic nanoparticles, which can be roughly divided into solid-phase method, liquid-phase method and gas-phase method according to the state of raw materials. The solid-phase method is a method in which metal salts or metal oxides are fully mixed according to a certain proportion, ground and calcined, and directly ground to nanoparticles after a solid-state reaction occurs, that is, high-energy mechanical ball milling. The method is simple to operate and low in cost. The disadvantage of this method is: during the preparation process, due to the wear of the ball, impurities are easily introduced into the powder, and the particle size distribution of the obtained powder is uneven. The sintering temperature of the ANNT system prepared by the traditional solid-state method is high, which may cause partial decomposition of the ANNT system and form many defects on the surface of the system, resulting in increased loss of the system.

Contents of Invention

In order to overcome the deficiencies in the prior art, the present invention provides a chemical preparation method of high dielectric constant ceramic material, aiming at preparing ANNT ceramic material with better dielectric properties by liquid phase method.

The liquid phase method is to prepare powder through the chemical reaction of liquid phase solution, which has the characteristics of precise control of product composition and content, and realization of mixing at the molecular or atomic scale. The obtained powder has narrow particle size distribution and regular shape, which is a method widely used in laboratories and industries. Synthetic powders may form severe agglomerates. In order to reduce the agglomeration phenomenon, in the state of solid-liquid mixing, all kinds of impurity ions remaining in the liquid phase should be removed as much as possible; and organic solvents such as alcohol and acetone with lower surface tension than water can be used to replace the water remaining between the particles. To obtain a powder with a lesser degree of agglomeration. During the precipitation process and the process of washing and dehydrating the precipitate, organic macromolecular surfactants, such as ammonium polyacrylate, polyethylene glycol, etc., are added. Due to the steric hindrance effect of organic macromolecules, the degree of agglomeration can be reduced. The methods of preparing nano-powders by liquid phase method mainly include precipitation method, spray pyrolysis method, sol-gel method and hydrothermal method. It is mainly suitable for the preparation of nano-oxides and multi-component substances.

The chemical preparation method of high dielectric constant ceramic material of the present invention comprises the steps:

1. Using analytically pure Ta ₂ O ₅ , Nb ₂ O ₅ , AgNO ₃ , and NaNO ₃ as raw materials, weigh Ta according to the composition of (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ in a specific ratio ₂ O ₅ , Nb ₂ O ₅ , add 100 mL of hydrofluoric acid, 100 mL of nitric acid, and heat in a water bath for 6-7 hours to completely dissolve Ta ₂ O ₅ and Nb ₂ O ₅ ;

2. Add 1:1.5 analytically pure citric acid (in terms of total moles of metal ions), until completely dissolved, to obtain a citric acid solution of Nb and Ta;

3. Weigh AgNO ₃ and NaNO ₃ according to the proportion, add distilled water to dissolve the two, add 1:1.5 analytically pure citric acid (calculated by the total number of moles of metal ions), mix well, and obtain a citric acid solution of Ag and Na , the two solutions were mixed, electromagnetically stirred for 2-4h, and a colorless transparent solution was obtained;

4. Bake it under an infrared lamp, and slowly evaporate the solvent. After 5 to 6 hours, a white powder block solid is obtained, which is the precursor of (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ body;

5. The precursor is milled by a ball mill for 3 hours, then heated to 400°C at a rate of 2°C/min, kept for 2 hours, and then burned at 700-950°C for 2 hours to obtain the required nano-powder.

High dielectric constant ceramic material of the present invention, the molar percentage of each component is:

AgNO ₃ 40-45%

_NaNO3 5-10%

Nb ₂ O ₅ 30-40%

Ta ₂ O ₅ 10-20%

Preferably:

AgNO ₃ 42-45%

_NaNO3 35-8%

Nb ₂ O ₅ 30-35%

Ta ₂ O ₅ 15-20%

The best values are:

AgNO ₃ 45%

_NaNO3 35%

Nb ₂ O ₅ 35%

Ta ₂ O ₅ 15%

Due to the high sintering temperature of the ANNT system prepared by the solid-state method, it may cause partial decomposition of the ANNT system and form many defects on the surface of the system, resulting in increased loss of the system. The liquid phase method can make the size of the powder in the nanometer, the size effect and the surface effect of the nanoparticle, so that the sintering temperature is reduced and the sintering rate is accelerated, which effectively suppresses the generation of system defects, and also controls the grain size and particle size. The uniformity of the liquid phase synthesis method can mix the raw materials at the molecular or atomic level, which is more uniform and more in line with the stoichiometric ratio. Therefore, compared with the solid-phase method, the crystal grains of the ceramic samples prepared by the liquid-phase method are more uniform, the particle size is smaller, and the dielectric properties are better. The liquid phase synthesis method can make the system uniformly mixed at the molecular level, effectively improve the sintering characteristics and microstructure of the system, reduce the sintering temperature of the system, reduce the defects in the system, and thus improve the dielectric properties of the system. The samples prepared by the solid-phase method had larger grains with uneven grain size distribution, while the average grain size of the samples prepared by the liquid-phase method was smaller, about hundreds of nanometers, and the distribution was very dense. Uniform, so the liquid phase method improves the structural characteristics of the system, which is the reason for the further improvement of the dielectric properties of the system.

Compared with the solid-phase synthesis method, the liquid-phase synthesis method of the present invention can obviously reduce the loss of the system, make the dielectric constant of the system higher and the absolute value of the temperature coefficient of capacitance smaller. When the Nb/Ta ratio is 0.8/0.2 and 0.7/0.3, the dielectric constant of the system reaches 540 and 538, the dielectric loss is small, and the temperature coefficient of capacitance reaches the range of 0±30ppm/℃, and the (high-frequency thermal Stability) Temperature characteristics of NP0.

Detailed ways

Comparative example 1

Adopt traditional solid state reaction method (Nb/Ta 0.8/0.2)

Ag ₂ O: 20g, Na ₂ CO ₃ : 1.5g, Nb ₂ O ₅ : 21g, Ta ₂ O ₅ : 7g were ball milled according to the corresponding proportions, and then calcined at 900°C to form a frit. The frit is added with binder paraffin, dry-pressed and sintered in the range of 1100-1150°C.

Comparative example 2

Adopt traditional solid phase reaction method (Nb/Ta 0.7/0.3)

Weigh Ag ₂ O: 20g, Na ₂ CO ₃ : 1.5g, Nb ₂ O ₅ : 19g, Ta ₂ O ₅ : 13g according to the corresponding proportions, and the others are the same as in Comparative Example 1 to prepare Nb/Ta 0.7/0.3 Porcelain.

Comparative example 3

Using traditional solid-state reaction method (Nb/Ta 0.6/0.4)

Weigh Ag ₂ O: 20g, Na ₂ CO ₃ : 1.5g, Nb ₂ O ₅ : 16g, Ta ₂ O ₅ : 18g according to the corresponding ratio, and the others are the same as in Comparative Example 1 to prepare Nb/Ta 0.6/0.4 Porcelain.

Example 1

Adopt liquid phase method (Nb/Ta 0.8/0.2) of the present invention

Using analytically pure Ta ₂ O ₅ , Nb ₂ O ₅ , AgNO ₃ , and NaNO ₃ as raw materials, weigh Ta ₂ O according to the composition of (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ in a specific ratio ₅ : 21g, Nb ₂ O ₅ : 7g, add 100mL of hydrofluoric acid, 100mL of nitric acid, and heat in a water bath for 6h to completely dissolve Ta ₂ O ₅ and Nb ₂ O ₅ . Add 1:1.5 analytically pure citric acid (calculated by the total number of moles of metal ions) until completely dissolved to obtain a citric acid solution of Nb and Ta. Weigh AgNO ₃ : 29g, NaNO ₃ : 2.4g according to the proportion, add distilled water to dissolve the two, add 1:1.5 analytically pure citric acid (calculated by the total moles of metal ions), and mix evenly to obtain Ag and Na. Citric acid solution, the two solutions were mixed, and electromagnetically stirred for 3 hours to obtain a colorless and transparent solution, which was baked under a 250W infrared lamp, and the solvent was slowly evaporated. After 5 hours, a white powder block solid was obtained, which is (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ precursor. The precursor was milled by a ball mill for 3 hours, then the temperature was raised to 400°C at a rate of 2°C/min, and kept for 2h. Then burn at 780°C for 2 hours to obtain the desired nanopowder.

Example 2

Adopt liquid phase method (Nb/Ta 0.7/0.3) of the present invention

Using analytically pure Ta ₂ O ₅ , Nb ₂ O ₅ , AgNO ₃ , and NaNO ₃ as raw materials, weigh Ta ₂ O according to the composition of (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ in a specific ratio ₅ : 13g, Nb ₂ O ₅ : 19g, add 100mL of hydrofluoric acid, 100mL of nitric acid, and heat in a water bath for 7h to completely dissolve Ta ₂ O ₅ and Nb ₂ O ₅ . Add 1:1.5 analytically pure citric acid (calculated by the total number of moles of metal ions) until completely dissolved to obtain a citric acid solution of Nb and Ta. Weigh AgNO ₃ : 29g and NaNO ₃ : 2.4g according to the proportion, add distilled water to dissolve the two, add 1:1.5 analytical pure citric acid, mix well, and obtain the citric acid solution of Ag and Na, mix the two solutions , electromagnetic stirring for 3 hours, a colorless transparent solution was obtained, which was baked under a 250W infrared lamp, and the solvent was slowly evaporated. After 6 hours, a white powder block solid was obtained, which is (Ag _x Na _1-x )[Nb _y Precursor of Ta _1-y ]O ₃ . The precursor was milled by a ball mill for 3 hours, then the temperature was raised to 400°C at a rate of 2°C/min, and kept for 2h. Then burn at 700°C for 2 hours to obtain the desired nanopowder.

Example 3

Adopt liquid phase method (Nb/Ta 0.6/0.4) of the present invention

Using analytically pure Ta ₂ O ₅ , Nb ₂ O ₅ , AgNO ₃ , and NaNO ₃ as raw materials, weigh Ta ₂ O according to the composition of (Ag _x Na _1-x )[Nb _y Ta _1-y ]O ₃ in a specific ratio ₅ : 18g, Nb ₂ O ₅ : 16g, add 100mL of hydrofluoric acid, 100mL of nitric acid, and heat in a water bath for 6h to completely dissolve Ta ₂ O ₅ and Nb ₂ O ₅ . Add 1:1.5 analytically pure citric acid (calculated by the total number of moles of metal ions) until completely dissolved to obtain a citric acid solution of Nb and Ta. Weigh AgNO ₃ : 29g and NaNO ₃ : 2.4g according to the proportion, add distilled water to dissolve the two, add 1:1.5 analytical pure citric acid, mix well, and obtain the citric acid solution of Ag and Na, mix the two solutions , electromagnetically stirred for 2 hours, a colorless transparent solution was obtained, which was baked under a 250W infrared lamp, and the solvent was evaporated slowly. After 5 hours, a white powder block solid was obtained, which is (Ag _x Na _1-x )[Nb _y Precursor of Ta _1-y ]O ₃ . The precursor was milled by a ball mill for 3 hours, then the temperature was raised to 400°C at a rate of 2°C/min, and kept for 2h. Then burn at 900°C for 2 hours to obtain the desired nanopowder.

The porcelain material in above-mentioned comparative example and embodiment is carried out the test of following electrical property, wherein

1. Calculation of dielectric constant of disk-shaped medium

Use HP4278A and HP4285A capacitor bridge to measure the capacitance C of the sample, and calculate the dielectric constant of the sample according to the formula (2-1).

$\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 14.4</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; d</span>}}{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where: C is the capacitance of the sample in pF.

D is the diameter of the sample, in cm.

d is the thickness of the sample, in cm.

2. Test of sample temperature characteristics and calculation of temperature coefficient

Using WAYNE KEER Multi Bridge 6425 testing instrument and GZ-ESPEC MC-710P high and low temperature cycle incubator to cooperate with each other, measure the capacitance of the sample at different temperatures, and complete the test of the temperature characteristics of the sample. The temperature coefficient of capacity of the material is calculated according to the following formula:

${\mathrm{\&alpha;}}_c=\frac{1}{C_0}\&Center\; Dot;\frac{C_1-C_0}{T_1-T_0}\&times;{10}^6$ (ppm/°C) (2-2)

Where: T ₀ - room temperature (25°C)

T ₁ - Test temperature (85°C)

C ₀ - Capacitance of the sample at T ₀ (PF)

C ₁ - Capacitance of the sample at temperature T ₁ (PF)

3. Measurement of sample insulation resistance and calculation of material volume resistivity

Use the ZC36 ultra-high resistance tester to measure the insulation resistance of the sample, and use the following formula to calculate the volume resistivity ρ _v of the material:

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Omega;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; cm</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Where: R _i - insulation resistance of the sample (Ω)

D-sample diameter (cm)

d-thickness of the sample (cm)

4. Measurement of sample dielectric loss

The dielectric loss tgδ(1MHz) of the sample was measured by HP4278A and HP4285A capacitance bridges. The resulting list is as follows:

Table 1 Effect of different synthesis methods on the dielectric properties of the system Nb/Ta resolve resolution Loss tangent tgδ(×10 ^-4 )(1MHz) Dielectric constantε(1MHz) Capacity temperature coefficient α _c (ppm/℃) Insulation resistivity ρ _v (Ω·cm) 0.8/0.2 Solid Phase 6.5 512 440 >10 ¹² liquid phase 4.2 540 20 >10 ¹² 0.7/0.3 Solid Phase 7.5 460 -421 >10 ¹² liquid phase 4.0 538 -6 >10 ¹² 0.6/0.4 Solid Phase 8.0 415 -760 >10 ¹² liquid phase 3.0 530 -460 >10 ¹²

Claims (4)

1. the chemical preparation process of a high-k porcelain comprises the steps:

(1) with (Ag _xNa _1-x) [Nb _yTa _1-y] O ₃Composition takes by weighing Ta by specified proportion ₂O ₅, Nb ₂O ₅, add hydrofluoric acid 100mL, nitric acid 100mL, heating in water bath 6～7h makes Ta ₂O ₅, Nb ₂O ₅Dissolving fully;

(2) the analytical pure citric acid (in the metal ion total mole number) that added 1: 1.5 extremely dissolves fully, has obtained the citric acid solution of Nb, Ta;

(3) take by weighing AgNO by proportioning ₃, NaNO ₃, adding distil water dissolves both, adds 1: 1.5 analytical pure citric acid (in the metal ion total mole number), mixes, and has obtained the citric acid solution of Ag, Na, and two kinds of solution are mixed, and induction stirring 2-4h has obtained colourless transparent solution;

(4) be placed on baking under the infrared lamp, slowly evaporating solvent obtains white powder agglomates shape solid behind 5～6h, and this is (Ag _xNa _1-x) [Nb _yTa _1-y] O ₃Presoma;

(5) presoma is through ball mill ball milling 3h, and the speed by 2 ℃/min is warming up to 400 ℃ again, insulation 2h, and then, promptly obtain desired nano-powder through 700～950 ℃ of calcination 2h.

2. a porcelain preparation method as claimed in claim 1 is characterized in that the molar content of described each component is

AgNO ₃ 340-45％

NaNO ₃ 35-10％

Nb ₂O ₅ 530-40％

Ta ₂O ₅ 10-20％

3. a porcelain preparation method as claimed in claim 2 is characterized in that the molar content of described each component is

AgNO ₃ 42-45％

NaNO ₃ 5-8％

Nb ₂O ₅ 30-35％

Ta ₂O ₅ 15-20％

4. a porcelain preparation method as claimed in claim 3 is characterized in that the molar content of described each component is

AgNO ₃ 45％

NaNO ₃ 5％

Nb ₂O ₅ 35％

Ta ₂O ₅ 15％