CN102503374A - Microwave dielectric ceramic Ba(4-x)SrxLiSb3O12 capable of being sintered at low temperature and preparation method thereof - Google Patents

Abstract

The invention discloses a microwave dielectric ceramic Ba(4-x)SrxLiSb3O12 capable of being sintered at low temperature and a preparation method thereof. A chemical formula of the dielectric ceramic provided by the invention is Ba(4-x)SrxLiSb3O12, wherein x is more than or equal to 0 but less than or equal to 4. The preparation method comprises the following steps: preparing raw powder of BaCO3, SrCO3, Li2CO3 and Sb2O3 with purity above 99.9% according to the formula of Ba(4-x)SrxLiSb3O12, wherein x is more than or equal to 0 but less than or equal to 4; wetly ball-milling and mixing for 12 hours; taking distilled water as a solvent; drying and then pre-sintering for 6 hours at 900 DEG C atmosphere; adding binder in the pre-sintered powder, and then pelleting; pressing and forming; and lastly, sintering for 4 hours at 950-1150 DEG C atmosphere, wherein a polyvinyl alcohol solution with a 5% mass concentration is taken as the binder, and the dosage of the binder is 2%-3% of the total weight of the pre-sintered powder. The ceramic prepared according to the preparation method provided by the invention is excellently sintered at 950-1150 DEG C; the dielectric constant is 28-40; the quality factor Qf value reaches up to 60000-100000GHz; and the resonant frequency temperature coefficient is small.

Description

But low-temperature sintered microwave dielectric ceramic Ba 4-xSr xLiSb 3O 12And preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to 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 is meant and is applied in microwave frequency band (mainly being UHF, the SHF frequency range) circuit as dielectric material and accomplishes the pottery of one or more functions; Be widely used as components and parts such as resonator, wave filter, dielectric substrate, medium guided wave loop in modern times in the 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 crucial application is arranged, just bringing into play increasing effect in the miniaturized of communication tool in modern times, the integrated process.

Be applied to the dielectric ceramic of microwave frequency band, should satisfy the requirement of following dielectric characteristics: the relative permittivity ε that (1) is high _rBe beneficial to miniaturization of devices, general requirement ε _r>=20; (2) high quality factor q value or dielectric loss tan δ are to reduce noise, general requirement Qf>=3000GHz; (3) the temperature factor τ of resonant frequency _rAs far as possible little of guaranteeing that device has good thermostability, general requirement-10/ ℃≤τ _r≤+10ppm/ ℃.In the world from late 1930s just the someone attempt dielectric substance is applied to microwave technology.

According to relative permittivity ε _rSize with use the different of frequency range, usually can be divided into 3 types by exploitation and the microwave-medium ceramics developed.

(1) low ε _rWith the microwave dielectric ceramic of high Q value, mainly be 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>=10GHz), τ _f≈ 0.Be mainly used in the microwave communication equipments such as direct broadcasting satellite of f >=8GHz as the dielectric resonance device.

(2) medium ε _rWith the microwave dielectric ceramic of Q value, mainly be 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 _f≤5ppm/ ℃.Be mainly used in interior microwave military radar of 4～8GHz range of frequency and the communication system as the dielectric resonance device.

(3) 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, and this also is the emphasis of microwave dielectric ceramic research.Since the eighties, physiognomy secondary such as Kolar, Kato are existing and studied perovskite-like tungsten bronze type BaO-Ln 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 ₃High ε such as system _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.

More than the sintering temperature of these material systems generally be higher than 1300 ℃, can not be directly and low melting point metal such as Ag, Cu burn the formation laminated 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, domestic and international research personnel have carried out exploring widely and studying to some low fever's system materials, mainly are to adopt sytull or glass-ceramic composite system; Because of low melting glass has higher relatively dielectric loss mutually, the existence of glassy phase has improved the dielectric loss of material greatly.Therefore the low fired microwave dielectric ceramic material of the no glassy phase of development is the emphasis of current research.But, still more limited for the system that is used for low fever's microwave-medium ceramics, this to a great extent limit the development of low temperature co-fired technology and microwave multilayer device.We disclose a kind of (Ba that consists of at the patent (ZL200610018112.5) in early stage _1-xSr _x) ₄LiNb _3-yTa _yO ₁₂, 0≤x≤1 wherein, but low fever's niobate dielectric ceramic of 0≤y≤2, its sintering temperature is lower than 1300 ℃, but the temperature factor τ of its resonant frequency _fBe worth highly slightly, limited its practical application.In order to obtain τ _fValue is near 0 material, and we are at stibnate Ba _4-xSr _xLiSb ₃O ₁₂In found serial hi-q, the temperature factor of resonant frequency more approaches 0 microwave dielectric ceramic.

Summary of the invention

The purpose of this invention is to provide a kind of have low-loss and good thermostability, have the high-frequency dielectric constant simultaneously and reach 28～40, the Qf value can be at 950～1150 ℃ of agglomerating microwave dielectric ceramic materials and preparation method thereof up to 60000～100000GHz.

Microwave dielectric ceramic material of the present invention consist of Ba _4-xSr _xLiSb ₃O12, wherein: 0≤x≤4.

Preparing method's concrete steps of this microwave dielectric ceramic material are:

Be the BaCO more than 99.9% at first with purity ₃, SrCO ₃, Li ₂CO ₃, Sb ₂O ₃Starting powder press Ba _4-xSr _xLiSb ₃O ₁₂Composition batching, wherein: 0≤x≤4; Wet ball-milling mixed 12 hours, and solvent is a zero(ppm) water, the pre-burning 6 hours in 900 ℃ of air atmosphere of oven dry back, in preburning powder, add sticker and granulation then after, compression moulding again, sintering 4 hours in 950～1150 ℃ of air atmosphere at last; Said sticker employing mass concentration is 5% polyvinyl alcohol solution, and dosage accounts for 2%～3% of preburning powder total amount.

The pottery of the present invention's preparation is good at 950-1150 ℃ of sintering, and its specific inductivity reaches 28～40, and quality factor q f value is up to 60000～100000GHz, and temperature coefficient of resonance frequency is little, and great using value is arranged in industry.

Embodiment

Table 1 shows several specific exampless and the microwave dielectric property thereof that constitutes each component content of the present invention.Its preparation method carries out the evaluation of microwave dielectric property as stated with the cylindrical dielectric resonator method.

This pottery can be widely used in the manufacturing that various dielectric resonances play microwave devices such as device, wave filter, can satisfy the Technology Need of systems such as mobile communication, satellite communications.

With the element such as the Ca of Ba, Sr analog structure and chemical property, Pb etc., also can make dielectric ceramic with analogous crystalline structure of the present invention and performance.

[table 1]

Claims (2)

1. but the application of a composite oxides conduct low-temperature sintered microwave dielectric ceramic is characterized in that consisting of of said composite oxides: Ba _4-xSr _xLiSb ₃O ₁₂, 0≤x≤4 wherein.

2. the preparation method of the composite oxides described in claim 1 is characterized in that concrete steps are: be the BaCO more than 99.9% with purity at first ₃, SrCO ₃, Li ₂CO ₃, Sb ₂O ₃Starting powder press Ba _4-xSr _xLiSb ₃O ₁₂Composition batching, wherein: 0≤x≤4; Wet ball-milling mixed 12 hours, and solvent is a zero(ppm) water, the pre-burning 6 hours in 900 ℃ of air atmosphere of oven dry back, in preburning powder, add sticker and granulation then after, compression moulding again, sintering 4 hours in 950～1150 ℃ of air atmosphere at last; Said sticker employing mass concentration is 5% polyvinyl alcohol solution, and dosage accounts for 2%～3% of preburning powder total amount.