CN102249670A - Low temperature sintered microwave dielectric ceramic Li2Ba1-xSrxTi4O16 and preparation method thereof - Google Patents

Abstract

The invention discloses a low temperature sintered microwave dielectric ceramic Li2Ba1-xSrxTi4O16 and a preparation method thereof. The components of the ceramic are shown in the formula of Li2Ba1-xSrxTi4O16, wherein x is more than or equal to 0 and less than or equal to 1. The preparation method comprises the following steps of: preparing raw materials of BaCO3, SrCO3, Li2CO3 and TiO2 original powder with the purity of over 99.9 percent according to the formula of Li2Ba1-xSrxTi4O16, wherein x is more than or equal to 0 and less than or equal to 1; mixing the prepared raw materials for 12 hours through wet ball-milling, wherein a solvent is distilled water; drying, and pre-sintering at 900DEG C in the air for 6 hours; adding an adhesive into the pre-sintered powder, granulating, and pressing for formation; and sintering at the temperature of between 950 and 1,050DEG C in the air for 4 hours, wherein the adhesive is a 5 mass percent polyvinyl alcohol solution and is 3 percent of the total weight of the pre-sintered powder. The ceramic is well sintered at the temperature of between 950 and 1,050DEG C, has the dielectric constant of 32-40, the quality factor Qf value of 60,000-100,000GHz, small temperature coefficient of resonance frequency, and great application value in industry.

Description

Low sintering microwave dielectric ceramic Li＜sub〉2＜/sub〉Ba＜sub〉1-x＜/sub〉Sr＜sub〉x＜/sub〉Ti＜sub〉4＜/sub〉O＜sub〉16＜/sub〉and 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 finishes the pottery of one or more functions, in modern communication, be widely used as components and parts such as resonator, wave filter, dielectric substrate, medium guided wave loop, 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, 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 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 _fAs far as possible little of guaranteeing that device has good thermostability, general requirement-10/ ℃≤τ _f≤+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, the microwave-medium ceramics that is developed He developing can be divided into 3 classes usually.

(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 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.

More than the sintering temperature of these material systems generally be higher than 1300 ℃, can not be directly and low melting point metals such as Ag, Cu burn the formation laminated ceramic capacitor altogether.In recent years, along with LTCC Technology (LowTemperature 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 be to adopt devitrified glass 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 has limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.

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 32～40, the Qf value can be at 950-1050 ℃ of agglomerating composite oxides microwave dielectric ceramic material Li up to 60000～100000GHz ₂Ba _1-xSr _xTi ₄O ₁₆And preparation method thereof.

The chemical constitution general formula of composite oxides microwave dielectric ceramic material of the present invention is: Li ₂Ba _1-xSr _xTi ₄O ₁₆, wherein: 0≤x≤1.

Above-mentioned composite oxides microwave dielectric ceramic material is prepared from as follows:

(1) with purity is BaCO more than 99.9% ₃, SrCO ₃, Li ₂CO ₃And TiO ₂Starting powder press Li ₂Ba _1-xSr _xTi ₄O ₁₆Form batching, wherein, 0≤x≤1;

(2) step (1) confected materials wet ball-milling was mixed 12 hours, solvent is a distilled water, the pre-burning 6 hours in 900 ℃ of air atmosphere of oven dry back, in preburning powder, add binding agent and granulation then after, compression moulding again, sintering 4h in 950-1050 ℃ of air atmosphere at last.

Described binding agent employing mass concentration is 5% polyvinyl alcohol solution, and dosage accounts for 3% of preburning powder total amount.

Microwave dielectric ceramic material of the present invention is good at 950-1050 ℃ of sintering, and its specific inductivity reaches 32～40, and quality factor q f value is up to 60000～100000GHz, and temperature coefficient of resonance frequency is little, industrial great using value is arranged.

Embodiment

Embodiment:

Table 1 shows several specific embodiments 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 mentioned above with the cylindrical dielectric resonator method.

Table 1:

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.

Claims (2)

1. composite oxides is characterized in that the chemical constitution general formula of described composite oxides is: Li as the application of microwave dielectric ceramic ₂Ba _1-xSr _xTi ₄O ₁₆, wherein≤x≤1.

2. the preparation method of composite oxides according to claim 1 is characterized in that concrete steps are:

(1) with purity is BaCO more than 99.9% ₃, SrCO ₃, Li ₂CO ₃And TiO ₂Starting powder press Li ₂Ba _1-xSr _xTi ₄O ₁₆Form batching, wherein, 0≤x≤1;

(2) step (1) confected materials wet ball-milling was mixed 12 hours, solvent is a distilled water, the pre-burning 6 hours in 900 ℃ of air atmosphere of oven dry back, in preburning powder, add binding agent and granulation then after, compression moulding again, sintering 4h in 950-1050 ℃ of air atmosphere at last;

Described binding agent employing mass concentration is 5% polyvinyl alcohol solution, and dosage accounts for 3% of preburning powder total amount.