CN103130505B - Low-temperature sinterable lithium-based microwave dielectric ceramic Li2W2O7 and preparation method thereof - Google Patents

Abstract

The invention discloses low-temperature sinterable lithium-based microwave dielectric ceramic Li2W2O7 and a preparation method thereof. The composition of the dielectric ceramic material is Li2W2O7. The preparation method comprises the following steps: (1) proportioning Li2CO3 having a purity of 99.9% or above and WO3 original powder according to Li2W2O7; (2) performing wet type ball milling and mixing on the raw materials in the step (1) for 12 hours by taking distilled water as solvent, drying, and then presintering at 450 DEG C in atmosphere for 6 hours; and (3) adding a binding agent into the powder prepared in the step (2), granulating, performing compression molding, and finally sintering at 510-530 DEG C in atmosphere for 4 hours, wherein the binding agent is a polyvinyl alcohol solution having a mass concentration of 5% and accounts for 3% of the total amount of the powder. The ceramic prepared by the invention can be favorably sintered at 510-530 DEG C, the dielectric constant is up to 13-14, the quality factor Qf value is up to 61000-68000 GHz, and the temperature coefficient of resonance frequency is low, thus ensuring that the invention has great application value industrially.

Description

Can low temperature sintering lithium-based microwave dielectric ceramics Li 2w 2o 7and preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to the microwave device such as dielectric resonator, filter used in microwave frequency, and the dielectric ceramic material of ceramic capacitor or temperature compensating capacitor and preparation method thereof.

Background technology

Microwave dielectric ceramic refers to and to be applied in microwave frequency band (mainly UHF, SHF frequency range) circuit as dielectric material and to complete the pottery of one or more functions, the components and parts such as resonator, filter, dielectric substrate, medium wave circuit are widely used as in modern communication, it is the key foundation material of modern communication technology, in portable mobile phone, automobile telephone, cordless telephone, telstar recipient, military radar etc., there is very important application, in the miniaturization, integrated process of modern communication instrument, just playing increasing effect.

Be applied to the dielectric ceramic of microwave frequency band, the requirement of following dielectric property should be met: (1) seriation DIELECTRIC CONSTANT ε _rto adapt to the requirement of different frequency and different application occasion; (2) high quality factor q value or dielectric loss tan δ to reduce noise, General Requirements Qf>=3000 GHz; (3) the temperature coefficient t of resonance frequency _flittle of as far as possible to ensure the thermal stability that device has had, General Requirements-10/ DEG C≤t _f≤+10 ppm/ DEG C.From late 1930s, just someone attempts dielectric substance to be applied to microwave technology in the world.

According to relative dielectric constant ε _rsize from use frequency range different, usually the microwave-medium ceramics be developed and developing can be divided into 4 classes.

(1) ultralow dielectric microwave dielectric ceramic, main representative is Al ₂o ₃-TiO ₂, Y ₂baCuO ₅, MgAl ₂o ₄and Mg ₂siO ₄deng, its ε _r≤ 20, quality factor q × f>=50000GHz, τ _?≤ 5 ppm/ ° C.Be mainly used in microwave base plate and high-end microwave device.

(2) low ε _rwith the microwave dielectric ceramic of high q-factor, mainly BaO-MgO-Ta ₂o ₅, BaO-ZnO-Ta ₂o ₅or BaO-MgO-Nb ₂o ₅, BaO-ZnO-Nb ₂o ₅system or the hybrid system MWDC material between them.Its ε _r=25 ~ 30, Q=(1 ~ 2) × 10 ⁴(under the GHz of f>=10), τ _?≈ 0.Be mainly used in the microwave communication equipments such as the direct broadcasting satellite of f >=8 GHz as dielectric resonance device.

(3) medium ε _rwith the microwave dielectric ceramic of Q value, mainly with BaTi ₄o ₉, Ba ₂ti ₉o ₂₀(Zr, Sn) TiO ₄deng the MWDC material for base, its ε _r=35 ~ 40, Q=(6 ~ 9) × 10 ³(under f=3 ~-4GHz), τ _?≤ 5 ppm/ ° C.Be mainly used in microwave military radar in 4 ~ 8 GHz frequency ranges and communication system as dielectric resonance device.

(4) high ε _rand the microwave dielectric ceramic that Q value is lower, be mainly used in civilian mobile communcations system in 0.8 ~ 4GHz frequency range, this is also the emphasis of microwave dielectric ceramic research.Since the eighties, the people such as Kolar, Kato in succession find and have studied perovskite-like tungsten bronze type BaO-Ln ₂o ₃-TiO ₂series (Ln=La, Sm, Nd, Pr etc. are called for short BLT system), complex perovskite structure CaO-Li ₂o-Ln ₂o ₃-TiO ₂series, lead base series material, Ca _1-xln _2x/3tiO ₃be contour ε _rmicrowave dielectric ceramic, the wherein BaO-Nd of BLT system ₂o ₃-TiO ₂material dielectric constant reaches 90, lead base series (Pb, Ca) ZrO ₃dielectric constant reaches 105.

The sintering temperature of these material systems is generally higher than 1300 ° of C above, can not directly and the low-melting-point metal such as Ag and Cu burn formation multilayer ceramic capacitor altogether.In recent years, along with LTCC Technology (Low Temperature Co-fired Ceramics, the requirement of development LTCC) and the development of microwave multilayer device, researcher both domestic and external has carried out exploring widely and studying to some low fever's system materials, mainly adopt devitrified glass or glassceramic composites system, because low-melting glass has relatively high dielectric loss mutually, the existence of glassy phase substantially increases the dielectric loss of material.Therefore development is the emphasis of current research without the low fired microwave dielectric ceramic material of glassy phase.But, still more limited for the system for low fever's microwave-medium ceramics, which greatly limits the development of low temperature co-fired technology and microwave multilayer device.

Can in the process of low fired microwave dielectric ceramic materials in exploration and development of new, the material systems such as the Li based compound that intrinsic sintering temperature is low, Bi based compound, tungstates architecture compound and tellurate architecture compound get the attention and research, wherein a large amount of exploratory developments concentrates on Li base binary or ternary compound, and have developed as Li ₂tiO ₃, Li ₃nbO ₄, Li ₂moO ₄and Li ₂mTi ₃o ₈serial microwave-medium ceramics of good performance etc. such as (M=Mg, Zn), document [Magarill, S.A., Klevtsova, R.F., Bakakin, V.V.; Crystal structure of lithium bitungstate Li ₂w ₂o ₇, Kristallografiya, 1973,18:269-276] and report Li base composite oxidate Li ₂w ₂o ₇crystal structure.Consider current document also not about Li ₂w ₂o ₇the preparation of pottery and the research of microwave dielectric property are reported, we are to Li ₂w ₂o ₇carried out sintering characteristic and Study on microwave dielectric property, found that this pottery have excellent comprehensive microwave dielectric property simultaneously sintering temperature lower than 550 °c, can be widely used in various medium substrate, manufacture that resonance plays the microwave device such as device and filter, can meet the technology needs of low temperature co-fired technology and microwave multilayer device.

Summary of the invention

The object of this invention is to provide and a kind ofly there is low-loss and good thermal stability, dielectric ceramic material with high-frequency dielectric constant and preparation method thereof simultaneously.

Dielectric ceramic material of the present invention consist of Li ₂w ₂o ₇.

Preparation method's step of this dielectric ceramic material is:

(1) be the Li of more than 99.9% by purity ₂cO ₃and WO ₃starting powder press Li ₂w ₂o ₇composition batching.

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 450 DEG C of air atmosphere after oven dry.

(3) in the powder that step (2) is obtained, binding agent is added and after granulation, more compressing, finally in 510 ~ 530 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the poly-vinyl alcohol solution of 5%, and dosage accounts for 3% of powder total amount.

Pottery prepared by the present invention is good at 510-530 DEG C of sintering, and its dielectric constant reaches 13 ~ 14, and quality factor q f value is up to 61000-68000GHz, and temperature coefficient of resonance frequency is little, industrially has great using value.

Embodiment

Embodiment:

Table 1 shows 3 specific embodiments and microwave dielectric property thereof that form different sintering temperature of the present invention.Its preparation method is described above, carries out the evaluation of microwave dielectric property by cylindrical dielectric resonator method.

The manufacture that this pottery can be widely used in various medium substrate, resonance plays the microwave device such as device, filter, can meet the technology needs of the system such as mobile communication, satellite communication.

The present invention is never limited to above embodiment, have with the element of V analog structure and chemical property as Mo and Cr etc. also can make with analogous crystalline structure of the present invention and performance dielectric ceramic.

Claims (1)

1. lithium base composite oxidate is as can the application of low-temperature sintered microwave dielectric ceramic, it is characterized in that consisting of of described lithium base composite oxidate: Li ₂w ₂o ₇;

Preparation method's step of described lithium base composite oxidate is:

(1) be the Li of more than 99.9% by purity ₂cO ₃and WO ₃starting powder press Li ₂w ₂o ₇composition batching;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 450 DEG C of air atmosphere after oven dry;

(3) in the powder that step (2) is obtained, binding agent is added and after granulation, more compressing, finally in 510 ~ 530 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the poly-vinyl alcohol solution of 5%, and dosage accounts for 3% of powder total amount.