CN103130505A - 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

But 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 devices such as the dielectric resonator that uses in microwave frequency, wave filter, and the dielectric ceramic material of ceramic condenser or thermo-compensation capacitor and preparation method thereof.

Background technology

Microwave dielectric ceramic refers to and is applied in microwave frequency band (being mainly UHF, SHF frequency range) circuit as dielectric material and completes the pottery of one or more functions, be widely used as the components and parts such as resonator, wave filter, dielectric substrate, medium guided wave loop in modern communication, it is the key foundation material of modern communication technology, at aspects such as portable mobile phone, automobile telephone, cordless telephone, telestar susceptor, military radars, very important application is arranged, in the miniaturization of modern communication instrument, integrated process, just bringing into play increasing effect.

Be applied to the dielectric ceramic of microwave frequency band, should meet the requirement of following dielectric characteristics: (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 are to reduce noise, general requirement Qf>=3000 GHz; (3) the temperature factor t of resonant frequency _fthe as far as possible little thermostability to guarantee that device has had, general requirement-10/ ℃≤t _f≤+10 ppm/ ℃.From late 1930s, just someone attempts dielectric substance is applied to microwave technology in the world.

According to relative permittivity ε _rsize from use the different of frequency range, usually the microwave-medium ceramics be developed He developing can be divided into to 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 value, be mainly BaO-MgO-Ta ₂o ₅, BaO-ZnO-Ta ₂o ₅or BaO-MgO-Nb ₂o ₅, BaO-ZnO-Nb ₂o ₅system or the composite system MWDC material between them.Its ε _r=25～30, Q=(1～2) * 10 ⁴(under f>=10 GHz), τ _?≈ 0.Be mainly used in the microwave communication equipments such as direct broadcasting satellite of f >=8 GHz as the dielectric resonance device.

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

(4) high ε _rand the lower microwave dielectric ceramic of Q value is mainly used in civilian mobile communcations system in 0.8～4GHz range of frequency, this is also the emphasis of microwave dielectric ceramic research.Since the eighties, the people such as Kolar, Kato find and have studied perovskite-like tungsten bronze type BaO-Ln in succession ₂o ₃-TiO ₂series (Ln=La, Sm, Nd, Pr etc., abbreviation 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 ₃specific inductivity reaches 105.

The sintering temperature of above these material systems is generally higher than 1300 ° of C, can not be directly and the low melting point metals such as Ag and Cu burn altogether the formation laminated ceramic capacitor.In recent years, along with LTCC Technology (Low Temperature Co-fired Ceramics, the requirement of development LTCC) and the development of microwave multilayer device, researchist both domestic and external has carried out exploring widely and studying to some low fever's system materials, mainly to adopt devitrified glass or glass-ceramic composite system, because low melting glass has relatively high dielectric loss mutually, the existence of glassy phase has improved the dielectric loss of material greatly.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, this has limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.

In exploration and development of new can be hanged down the process of fired microwave dielectric ceramic materials, the material systems such as the Li based compound that intrinsic sintering temperature is low, Bi based compound, tungstate architecture compound and tellurate architecture compound get the attention and study, wherein a large amount of exploratory developments concentrates on Li base binary or ternary compound, and has developed as Li ₂tiO ₃, Li ₃nbO ₄, Li ₂moO ₄and Li ₂mTi ₃o ₈serial well behaved microwave-medium ceramics such as (M=Mg, Zn) etc., 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 reported Li base composite oxidate Li ₂w ₂o ₇crystal structure.Consider that current document is not also about Li ₂w ₂o ₇the preparation of pottery and the research of microwave dielectric property report, we are to Li ₂w ₂o ₇carried out sintering characteristic and Study on microwave dielectric property, found that this pottery has excellent comprehensive microwave dielectric property while sintering temperature lower than 550 °c, can be widely used in the manufacture that various medium substrates, resonance play the microwave devices such as device and wave filter, can meet the Technology Need of low temperature co-fired technology and microwave multilayer device.

Summary of the invention

The purpose of this invention is to provide a kind of have low-loss and good thermostability, there is dielectric ceramic material of 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) by purity, be the Li more than 99.9% 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 ℃ of air atmosphere after oven dry.

(3) after adding binding agent granulation in the powder made in step (2), then compression moulding, last sintering 4 hours in 510 ~ 530 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total amount.

Pottery prepared by the present invention is good at 510-530 ℃ of sintering, and its specific inductivity reaches 13～14, and quality factor q f value is up to 61000-68000GHz, and temperature coefficient of resonance frequency is little, industrial great using value is arranged.

Embodiment

Embodiment:

Table 1 shows 3 specific embodiments and the microwave dielectric property thereof that forms different sintering temperatures of the present invention.Its preparation method as mentioned above, carries out the evaluation of microwave dielectric property by the cylindrical dielectric resonator method.

This pottery can be widely used in the manufacture that various medium substrates, resonance play the microwave devices such as device, wave filter, can meet the Technology Need of the systems such as mobile communication, satellite communications.

The present invention never is 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. but a lithium base composite oxidate, as the application of low-temperature sintered microwave dielectric ceramic, 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) by purity, be the Li more than 99.9% 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 ℃ of air atmosphere after oven dry;

(3) after adding binding agent granulation in the powder made in step (2), then compression moulding, last sintering 4 hours in 510 ~ 530 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total amount.