CN107777997A - A kind of preparation method of the high Qf values microwave-medium ceramics of medium dielectric constant microwave medium - Google Patents

Abstract

The invention discloses a method for preparing microwave dielectric ceramics with medium dielectric constant and high Qf value. BaCO ₃ , CoO, ZnO, and Nb ₂ O ₅ are first prepared according to the stoichiometric formula Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _{2/ 3} ] O ₃ for batching, after ball milling, drying, and sieving, put it into an alumina crucible and seal the crucible lid, pre-fire at 1000-1200 ° C, and then pressure-form after ball milling, drying, and sieving Green body, then put the green body in a closed alumina crucible, use upright or inverted sintering methods, sinter at 1350 ° C ~ 1450 ° C, and then cool down to 1000 °C at a cooling rate of 1 ° C / min ~ 0.05 ° C / min ~1200℃, made of microwave dielectric ceramics with medium dielectric constant and high Qf value. The dielectric constant ε _r of the present invention is 30-33, and the optimum Qf value is 99000. The method simplifies the preparation process and saves time and energy costs.

Description

A method for preparing microwave dielectric ceramics with medium dielectric constant and high Qf value

technical field

The invention belongs to a ceramic composition characterized by components, in particular to a preparation method with Ba[(Co _0.7 Zn _0.3 ) _{1/ 3} Nb _2/3 ]O ₃ as the chemical formula and improving its Qf value.

Background technique

Microwave dielectric ceramics are key materials for realizing microwave waveguiding, shielding and resonance. They have the advantages of low loss, high dielectric constant, and high resonance frequency stability, etc., and provide important material support for the rapid development of microwave technology. Microwave dielectric ceramics are widely used in components such as oscillators, resonators, filters, phase shifters, microwave substrates, and microwave antennas in microwave technology. Among them, the dielectric resonance function is the main function realized by microwave dielectric ceramics. Dielectric resonators made of microwave dielectric ceramics have many advantages, such as small size, light weight, and low loss. Correspondingly, microwave technology equipment can be miniaturized, Portability and high quality.

With the rapid development of microwave technology, the application of microwave dielectric ceramics in emerging fields continues to emerge, such as global positioning system, wireless local area network, digital TV and the fifth generation of mobile communication. Therefore, microwave dielectric ceramics are in the ascendant, and their development prospects are still very broad. At present, miniaturization, low loss, high stability, chip type and low cost are the development direction of microwave dielectric ceramic components, and also the development direction of dielectric resonators, and the development of devices is inseparable from high-performance microwave dielectric materials. support. In recent years, the Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _2/3 ]O ₃ material system with a composite perovskite structure has been favored due to its moderate dielectric constant (~30), low dielectric loss (Qf >50,000) is a research hotspot. However, due to poor thermal stability, most niobates will undergo disordered phase transition during sintering, and the dielectric loss is large, so the subsequent heat treatment process is essential. For To further reduce the dielectric loss of the material system (increase its Qf value), it is necessary to further optimize and improve its preparation process.

Contents of the invention

The purpose of the present invention is to increase the Qf value of Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _2/3 ]O ₃ to meet the needs of the development of microwave dielectric ceramics with low loss. Using BaCO ₃ , CoO, ZnO, and Nb ₂ O ₅ as raw materials, a microwave dielectric ceramic with medium dielectric constant and high Qf was prepared by a simple solid-state method.

The present invention is realized through the following technical solutions.

A method for preparing microwave dielectric ceramics with medium dielectric constant and high Qf value, the specific implementation steps are as follows:

(1) Dosing BaCO ₃ , CoO, ZnO, Nb ₂ O ₅ according to the stoichiometric formula Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _2/3 ]O ₃ ; put the powder into the polyester tank, After adding absolute ethanol and zirconium balls, ball mill for 4 to 12 hours;

(2) Put the ball-milled raw materials in step (1) into a drying oven, dry them at 80-100°C, and pass through a 40-mesh sieve;

(3) Put the dried and sieved powder into an alumina crucible, cover the crucible and seal it, then put it in a medium-temperature furnace, pre-fire it at 1000-1200°C, and keep it warm for 3-6 hours;

(4) Put the pre-burned powder in step (3) into a ball mill jar, add zirconia balls and absolute ethanol, ball mill for 10 to 15 hours, sieve after drying, and then use a powder tablet press to 1 ~3MPa pressure pressed into green body;

(5) Put the green body of step (4) in a closed alumina crucible, adopt two sintering methods: upright or upside down, sinter at 1350°C-1450°C, keep warm for 6-18 hours, and then sinter at 1°C/min- The cooling rate of 0.05°C/min is lowered to 1000-1200°C, and a microwave dielectric ceramic with a medium dielectric constant and a high Qf value is produced.

The ball milling time of the step (1) is 8 hours.

The holding time of the step (5) is 12 hours, and then the temperature is lowered to 1100° C. at a cooling rate of 0.2° C./min.

The invention prepares microwave dielectric ceramics with medium dielectric constant and high Qf through solid-phase method combined with appropriate sintering mode, holding time, cooling rate and temperature. Its dielectric constant ε _r is 30-33, and the best Qf value is 99000. The method simplifies the preparation process and saves time and energy costs.

Detailed ways

The invention uses BaCO ₃ , CoO, ZnO, and Nb ₂ O ₅ as initial raw materials, and prepares microwave dielectric ceramic materials with medium dielectric constant and high Qf value through a solid phase method. Specific examples are as follows:

Example 1

1. Mix BaCO ₃ , CoO, ZnO, and Nb ₂ O ₅ according to the stoichiometric formula Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _2/3 ]O ₃ , and the ratio is: 14.9497g BaCO ₃ , 1.3179g CoO, 0.6167gZnO, 6.6459gNb ₂ O ₅ Put 20g of the mixed powder into a nylon tank, add 200ml of absolute ethanol, and then add 150g of zirconium balls, and ball mill on a planetary ball mill for 8 hours at a speed of 400 rpm Minute;

2. Place the ball-milled raw materials in a drying oven, dry them at 80°C, and then pass them through 40-mesh sieves;

3. Put the dried and sieved powder into a sealed alumina crucible, place it in a medium-temperature furnace for pre-burning at 1100°C, and keep it warm for 4 hours;

4. Mix the pre-fired powder in step 3 according to the stoichiometric formula Ba[(Co _0.7 Zn _0.3 ) _1/3 Nb _2/3 ]O ₃ +0.7wt%PVA, put it into a ball mill jar, and add zirconia Balls and absolute ethanol, ball milled for 12 hours, dried and sieved, and then pressed into a green body with a powder tablet press at a pressure of 2 MPa;

5. Put the green body in the upright alumina, conduct airtight sintering at 1400°C, keep it warm for 12 hours, and then cool it down to 1100°C at a cooling rate of 0.2°C/min to make a medium dielectric constant with low loss and high Qf Value microwave dielectric ceramics.

6. Test its microwave dielectric properties with a network analyzer, and its properties are as follows:

Dielectric constant: 30.9

Quality factor: 99354

Resonant frequency temperature coefficient: 12ppm/℃

Embodiment 2-8

The main process parameters and microwave dielectric properties of Examples 2-8 are detailed in Table 1, and the rest of the preparation process is exactly the same as that of Example 1.

Table 1

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

Claims (3)

1. a kind of preparation method of the high Qf values microwave-medium ceramics of medium dielectric constant microwave medium, specific implementation step are as follows：

(1) by BaCO₃、CoO、ZnO、Nb₂O₅Stoichiometrically formula Ba [(Co_0.7Zn_0.3)_1/3Nb_2/3]O₃Carry out dispensing；Powder is put Enter in polyester tank, after adding absolute ethyl alcohol and zirconium ball, ball milling 4~12 hours；

(2) raw material after step (1) ball milling is put into drying box, in 80~100 DEG C of drying, then crosses 40 mesh sieves；

(3) powder after drying, sieving is put into alumina crucible and covered crucible lid seals, and is subsequently placed in moderate oven, in 1000~1200 DEG C of pre-burnings, it is incubated 3~6 hours；

(4) by the powder after step (3) pre-burning, it is put into ball grinder, adds zirconia ball and absolute ethyl alcohol, ball milling 10~15 are small When, sieved after drying, then base substrate is pressed into 1~3MPa pressure with powder compressing machine；

(5) green compact of step (4) are placed in closed alumina crucible, using it is upright or stand upside down two kinds of sintering processings, in 1350 DEG C~1450 DEG C sintering, are incubated 6~18 hours, are cooled to afterwards with 1 DEG C/min~0.05 DEG C/min rate of temperature fall 1000~1200 DEG C, the microwave-medium ceramics of the high Qf values of medium dielectric constant microwave medium are made.

2. a kind of preparation method of the high Qf values microwave-medium ceramics of medium dielectric constant microwave medium according to claim 1, its feature exist In the Ball-milling Time of the step (1) is 8 hours.

3. a kind of preparation method of the high Qf values microwave-medium ceramics of medium dielectric constant microwave medium according to claim 1, its feature exist In the soaking time of the step (5) is 12h, afterwards using rate of temperature fall as 0.2 DEG C/min, is cooled to 1100 DEG C.