CN105347795A - High-quality factor lithium-magnesium-niobium-series microwave dielectric ceramic - Google Patents

Abstract

The invention discloses high-quality factor lithium-magnesium-niobium-series microwave dielectric ceramic. The ceramic has a chemical formula of Li3(Mg0.95A0.05)2NbO6, wherein A=Ca<2+>, Ni<2+>, Zn<2+> and Mn<2+>. Li2CO3, MgO, CaCO3, NiCO3, ZnO, MnCO3 and Nb2O5 are blended according to the chemical formula, is subjected to ball mill, drying and sieving, the powder is subjected to calcining, secondary ball milling and granulation, the granules are pressed to form a blank, and the blank is sintered at a temperature of 1120-1180 DEG C to form the lithium-magnesium-niobium-series microwave dielectric ceramic. The lithium-magnesium-niobium-series microwave dielectric ceramic has dielectric constant of 12.29-15.62, a quality factor of 52700-96160 GH and a resonant frequency temperature coefficient of -23.08 to -18.47ppm/DEG C, can be prepared by simple and eco-friendly processes and has a use prospect.

Description

A High Quality Factor Lithium Magnesium Niobium Microwave Dielectric Ceramic

technical field

The invention belongs to a ceramic composition characterized by components, in particular to a lithium-magnesium-niobium series microwave dielectric ceramic with high quality factor and a preparation method thereof.

Background technique

With the development of microwave communication technology, microwave dielectric ceramic materials have attracted more and more attention, and suitable dielectric constant, high quality factor and good resonant frequency temperature coefficient are microwave dielectric ceramic materials that can be used in microwave There are three necessary requirements in the device, and these three parameters correspond to the size, operating frequency and thermal stability of the device made of the material. In terms of current applications, microwave dielectric ceramic materials are increasingly used in high-performance microwave components such as resonators, filters and dielectric antennas, and their role is becoming more and more important. Therefore, research on the functionality of new microwave dielectric ceramic materials is urgently needed.

The Li ₃ Mg ₂ NbO ₆ -series microwave dielectric ceramics with a rock-salt structure is a new type of microwave dielectric ceramic that has just been developed recently. It has good microwave dielectric properties, with a dielectric constant of 16.8, a quality factor of 796430GHz, and a resonance frequency temperature coefficient of -27.2ppm/°C.

But there are few reports on its preparation method and modification. The present invention adopts the traditional solid phase method, and uses different divalent metal ions (Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ) to replace the Mg ions in Li ₃ Mg ₂ NbO ₆ ceramics respectively, so as to ensure the On the basis of keeping the electrical constant basically unchanged, the quality factor of neodymium niobate ceramics is greatly improved, and at the same time, its resonant frequency temperature coefficient is improved to a certain extent, making it an ideal microwave dielectric ceramic material.

Contents of the invention

The object of the present invention is to ensure that its dielectric constant remains basically unchanged, greatly improve its quality factor, and at the same time improve its resonance frequency temperature coefficient to a certain extent on the basis of the prior art, and provide a kind _{of Li2CO3} , MgO and Nb ₂ O ₅ are the main raw materials, and magnesium ions are replaced by appropriate amount of divalent metal ions (Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ) to prepare lithium magnesium with high quality factor Q×f Niobium series microwave dielectric ceramics.

The present invention is realized through the following technical solutions.

1. A lithium-magnesium-niobium series microwave dielectric ceramic with a high quality factor, its composition is Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ , where A=Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ;

The preparation method of the above-mentioned lithium-magnesium-niobium series microwave dielectric ceramics has the following steps:

(1) Mix Li ₂ CO ₃ , MgO, CaCO ₃ , NiCO ₃ , ZnO, MnCO ₃ , Nb ₂ O ₅ raw materials, Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ , where A=Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ; according to the ratio of raw materials: deionized water: ball mass ratio of 2:16:15, add it into the polyester tank, and mill it on the ball mill for 6 hours;

(2) Place the ball-milled raw materials in step (1) in a drying oven to dry at 120° C., and pass through a 40-mesh sieve after drying to obtain a powder with uniform particles;

(3) Calcining the homogeneously mixed powder in step (2) at 1050° C. for 4 hours;

(4) the ceramic powder after step (3) is calcined is put into polyester pot, after adding deionized water and zirconia ball, ball mills on the ball mill for 6 hours; Add weight percentage in ceramic powder after drying: 6-8% paraffin is used as a binder for granulation, passed through an 80-mesh sieve, and then formed into a green body with a powder tablet press;

(5) Sintering the green body in step (4) at 1120-1180° C. and keeping it warm for 4 hours to obtain microwave dielectric ceramics.

The purity of the raw materials Li ₂ CO ₃ , MgO, CaCO ₃ , NiCO ₃ , ZnO, MnCO ₃ and Nb ₂ O ₅ in the step (1) is greater than 99%.

The ball mill in the step (1) and step (4) is a planetary ball mill.

The working pressure of the tablet press of described step (4) is 7MPa.

The specification of the green body in the step (4) is a cylinder of Φ10mm×5mm.

The sintering temperature of the step (5) is 1140° C., and the temperature is kept for 4 hours.

The beneficial effects of the present invention are as follows:

_{Li 3 (} ^{Mg 0.95} _A ^0.05 _{) 2} ^NbO _{6 (} Where A=Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ) microwave dielectric ceramics. When the sintering temperature is 1140°C, the holding time is 4h, the first ball milling time and the second ball milling time are both 6h, and A is Ca ²⁺ ions, the dielectric constant is 15.62, the temperature coefficient of resonance frequency reaches -18.47ppm/°C, and the quality factor The maximum value reached is 96160GHz. Since partial ion substitution promotes the growth of its crystal grains and reduces its pores, the quality factor is improved. In addition, the preparation process is simple, the process is environmentally friendly, and the preparation is simple, which is a promising microwave dielectric material.

detailed description

The invention adopts chemical raw materials Li ₂ CO ₃ , MgO, CaCO ₃ , NiCO ₃ , ZnO, MnCO ₃ and Nb ₂ O ₅ with a purity greater than 99% to prepare a novel low-loss microwave dielectric ceramic material Li ₃ Mg ₂ NbO ₆ .

In the present invention, Li ₂ CO ₃ , MgO, CaCO ₃ , NiCO ₃ , ZnO, MnCO ₃ , and Nb ₂ O ₅ raw materials are formulated according to the chemical formula Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ²⁺ ) for batching, materials: deionized water: grinding ball = 2:16:15 ratio into polyester tank, ball milling for 6 hours; the raw material after ball milling is placed in an infrared drying box Dry at 120°C, pass through a 40-mesh sieve, and then calcined at 1050°C for 4 hours; then put the calcined ceramic powder into a ball mill jar, add zirconia balls and deionized water ball mill for 6 hours, and then dry; The dried ceramic powder is granulated by adding a paraffin wax binder with a weight percentage of 6-8%. After passing through an 80-mesh sieve, use a powder tablet machine to press the powder into a diameter of 10mm and a thickness of 10mm under a pressure of 7MPa. It is a 5mm green body; the green body is sintered at 1120-1180°C and held for 4 hours to obtain a lithium-magnesium-niobium-based microwave dielectric ceramic; finally, the microwave dielectric properties of the product are tested by a network analyzer.

Specific examples of the present invention are as follows.

Example 1:

1. According to Li ₂ CO ₃ -6.7107g, MgO-4.6365g, CaCO ₃ -0.6060 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ca ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.0468g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1140°C and keep it warm for 4 hours to prepare lithium magnesium niobium series Li ₃ (Mg _0.95 Ca _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Example 2:

1. According to Li ₂ CO ₃ -6.6731g, MgO-4.6105g, NiCO ₃ -0.7147 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ni ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.0017g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1140°C and keep it warm for 4 hours to obtain lithium magnesium niobium series Li ₃ (Mg _0.95 Ni _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Embodiment 3:

1. According to Li ₂ CO ₃ -6.7489g, MgO-4.6629g, ZnO-0.4956g according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Zn ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics , Nb ₂ O ₅ -8.0926g ingredients, 20g in total; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1140°C and keep it warm for 4 hours to prepare Li ₃ (Mg _0.95 Zn _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Embodiment 4:

1. According to Li ₂ CO ₃ -6.6806g, MgO-4.6157g, MnCO ₃ -0.6928 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Mn ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.00108g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1140°C and keep it warm for 4 hours to prepare Li ₃ (Mg _0.95 Mn _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Embodiment 5:

1. According to Li ₂ CO ₃ -6.7107g, MgO-4.6365g, CaCO ₃ -0.6060 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ca ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.0468g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1120°C and keep it warm for 4 hours to prepare lithium magnesium niobium series Li ₃ (Mg _0.95 Ca _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Embodiment 6:

1. According to Li ₂ CO ₃ -6.7107g, MgO-4.6365g, CaCO ₃ -0.6060 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ca ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.0468g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; use a powder tablet press to press into a green body with a diameter of 10mm and a thickness of 5mm with a pressure of 7MPa;

5. Sinter the green body at 1160°C and keep it warm for 4 hours to prepare lithium magnesium niobium series Li ₃ (Mg _0.95 Ca _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

Embodiment 7:

1. According to Li ₂ CO ₃ -6.7107g, MgO-4.6365g, CaCO ₃ -0.6060 according to Li ₃ (Mg _0.95 A _0.05 ) ₂ NbO ₆ (wherein A=Ca ²⁺ ) components of lithium-magnesium-niobium microwave dielectric ceramics g, Nb ₂ O ₅ -8.0468g ingredients, a total of 20g; the mixed powder was added to the polyester tank, after adding 160ml deionized water and 150g zirconium balls, ball milled on a planetary ball mill for 6 hours, and the speed of the ball mill was 1000 rpm ;

2. Put the ball-milled raw material in a drying oven, dry at 120°C and pass through a 40-mesh sieve to obtain a powder with uniform particles;

3. Calcinate the powder at 1050°C for 4 hours;

4. Put the calcined powder into a polyester tank, ball mill it for 6 hours for the second time, dry it after discharge, and pass through a 40 mesh sieve; then add 6% paraffin wax as a binder for granulation, and Pass through an 80-mesh sieve; then use a powder tablet press with a pressure of 7MPa to press into a green body with a diameter of 10mm and a thickness of 5mm;

5. Sinter the green body at 1180°C and keep it warm for 4 hours to prepare lithium magnesium niobium series Li ₃ (Mg _0.95 Ca _0.05 ) ₂ NbO ₆ microwave dielectric ceramics;

Finally, the microwave characteristics of the obtained samples were tested by a network analyzer.

See Table 1 for details of the key parameters and the detection results of the dielectric properties of the specific embodiments of the present invention.

Table 1

The detection method of the embodiment of the present invention is as follows:

1. The diameter and thickness of the sample are measured using a micrometer.

2. With the help of Agilent8720ES network analyzer, use the parallel plate method to measure the power saving constant of the prepared cylindrical ceramic material, put the test fixture into the ESPECMC-710F high and low temperature cycle incubator to measure the temperature coefficient of resonant frequency, the temperature range The test frequency is in the range of 8-12GHz for 25-85°C.

3. The quality factor of the prepared cylindrical ceramic samples is measured by the closed cavity method, and the test frequency is in the range of 6-10 GHz.

The present invention is not limited to the above-described embodiments, and changes in many details are possible without thereby departing from the scope and spirit of the present invention.

Claims (6)

1. a high quality factor lithium magnesium niobium series microwave dielectric ceramic, it consists of Li ₃(Mg _0.95a _0.05) ₂nbO ₆, wherein A=Ca ²⁺, Ni ²⁺, Zn ²⁺, Mn ²⁺.

The preparation method of above-mentioned lithium magnesium niobium series microwave dielectric ceramic, has following steps:

(1) by Li ₂cO ₃, MgO, CaCO ₃, NiCO ₃, ZnO, MnCO ₃, Nb ₂o ₅raw material, Li ₃(Mg _0.95a _0.05) ₂nbO ₆prepare burden, wherein A=Ca ²⁺, Ni ²⁺, Zn ²⁺, Mn ²⁺; In raw material: deionized water: mill ball quality adds in polyester tank than the ratio for 2:16:15, ball milling 6 hours on ball mill;

(2) raw material after step (1) ball milling is placed in loft drier in 120 DEG C of oven dry, crosses 40 mesh sieves after drying, obtain evengranular powder;

(3) powder step (2) mixed was in 1050 DEG C of calcinings 4 hours;

(4) ceramic powder after step (3) being calcined puts into polyester tank, after adding deionized water and zirconia ball, and ball milling 6 hours on ball mill; After oven dry in ceramic powder added weight per-cent be 6 ~ 8% paraffin carry out granulation as tackiness agent, cross 80 mesh sieves, then be shaped to base substrate with powder compressing machine;

(5) just walk the green compact of (4) again in 1120 ~ 1180 DEG C of sintering, be incubated 4 hours, obtained microwave-medium ceramics.

2. a kind of low-loss lithium magnesium niobium series microwave dielectric ceramic according to claim 1, is characterized in that, the raw material Li of described step (1) ₂cO ₃, MgO, CaCO ₃, NiCO ₃, ZnO, MnCO ₃, Nb ₂o ₅purity be greater than 99%.

3. a kind of low-loss lithium magnesium niobium series microwave dielectric ceramic according to claim 1, it is characterized in that, described step (1) and step ball mill are (4) planetary ball mill.

4. a kind of low-loss lithium magnesium niobium series microwave dielectric ceramic according to claim 1, it is characterized in that, the operating pressure of the tabletting machine of described step (4) is 7MPa.

5. a kind of low-loss lithium magnesium niobium series microwave dielectric ceramic according to claim 1, it is characterized in that, the green compact specification of described step (4) is the right cylinder of Φ 10mm × 5mm.

6. a kind of low-loss lithium magnesium niobium series microwave dielectric ceramic according to claim 1, it is characterized in that, the sintering temperature of described step (5) is 1140 DEG C, is incubated 4 hours.