CN103193483A - Low-temperature sintering tungstate microwave dielectric ceramic Li3R3W2O12 and preparation method thereof - Google Patents

Abstract

The invention discloses low-temperature sintering tungstate microwave dielectric ceramic Li3R3W2O12 and a preparation method thereof. The low-temperature sintering tungstate microwave dielectric ceramic material comprises the components of Li3R3W2O12, wherein R is one of Nd, La and Sm. The method comprises the steps of (1) weighing and dosing the original powder of Li2CO3, R2O3 and WO3, of which the purity is more than 99.9% according to the chemical formula of Li3R3W2O12, wherein R is one of Nd, La and Sm; (2) mixing the materials for 12 hours in a wet ball grinding manner, wherein the solvent is distilled water, and pre-sintering for 6 hours after baking in the atmosphere of 800 DEG C; and (3) adding a binder to the prepared powder and pelletizing, then pressing and molding, and finally sintering for 4 hours in the atmosphere of 850-900 DEG C, wherein the binder adopts polyvinyl alcohol solution of which the mass concentration is 5%; and the dosage is 3% of the total weight of the powder. The ceramic prepared by the preparation method has good sintering property at 850-900 DEG C; the dielectric constant achieves 20-22; the quality factor Qf value can be up to 57000-76000GHz; and the resonant frequency temperature coefficient is small.

Description

But low-temperature sintering tungstate microwave dielectric ceramic Li 3r 3w 2o 12and preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to microwave dielectric ceramic material of the microwave devices such as medium substrate, resonator and wave filter that use in microwave frequency 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 and 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 and 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 τ of resonant frequency _?the as far as possible little thermostability to guarantee that device has had, general requirement-10/ ℃≤τ _?≤+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 _?≤ 10 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 or 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 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.

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 or Zn) etc., but but low fever's microwave-medium ceramics system is still more limited, and this has limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.We are to consisting of Li ₃r ₃w ₂o ₁₂the Li base tungstate ceramics of (R=Nd, La or Sm) has carried out sintering characteristic and Study on microwave dielectric property, found that such pottery has excellent comprehensive microwave dielectric property while sintering temperature lower than 950 °c, can be widely used in the manufacture of the microwave devices such as various resonators and wave filter, can meet the needs 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, microwave dielectric ceramic material that sintering temperature is low simultaneously and preparation method thereof.

Microwave dielectric ceramic material of the present invention consist of Li ₃r ₃w ₂o ₁₂, wherein R is a kind of in Nd, La and Sm.

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

(1) by purity, be the Li more than 99.9% ₂cO ₃, R ₂o ₃and WO ₃starting powder press Li ₃r ₃w ₂o ₁₂the chemical formula weigh batching, wherein R is a kind of in Nd, La and Sm;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 800 ℃ 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 850 ~ 900 ℃ 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 650-700 ℃ of sintering, and its specific inductivity reaches 20～22, and quality factor q f value is up to 57000-76000GHz, and temperature coefficient of resonance frequency is little, industrial great using value is arranged.

Embodiment

Embodiment:

Table 1 shows and forms different 6 specific embodiments and the microwave dielectric property thereof formed with sintering temperature of the present invention.Its preparation method as mentioned above, carries out the evaluation of microwave dielectric property by the cylindrical dielectric resonator method.

The present invention never is limited to above embodiment.The bound of sintering temperature, interval value can realize the present invention, at this, do not enumerate embodiment.

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

Table 1:

Claims (1)

1. but a tungstate, as the application of low-temperature sintered microwave dielectric ceramic, is characterized in that the chemical constitution general formula of described tungstate is: Li ₃r ₃w ₂o ₁₂, wherein R is a kind of in Nd, La and Sm;

Preparation method's concrete steps of described tungstate are:

By purity, be the Li more than 99.9% ₂cO ₃, R ₂o ₃and WO ₃starting powder press Li ₃r ₃w ₂o ₁₂the chemical formula weigh batching, wherein R is a kind of in Nd, La and Sm;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 800 ℃ 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 850 ~ 900 ℃ 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.