CN104649666A - Temperature-stable tungstate microwave dielectric ceramic capable of being sintered at low temperature - Google Patents

Abstract

The invention provides temperature-stable tungstate microwave dielectric ceramic capable of being sintered at low temperature, and a preparation method thereof. The ceramic comprises the following components: (1-x)Li2Mg2W2O9+xCaTiO3, wherein x is more than or equal to 2% and less than or equal to 10%, and x is mole percent. The ceramic can be sintered at the temperature of 950DEG C below, and meet the cofiring requirement of low-cost silver electrodes, and has microwave performance; the dielectric constant reaches 15-24, Qf value is high (60000-78000GHz), the temperature coefficient of resonance frequency is small, and the ceramic can be used for manufacturing a low-temperature cofired ceramic system, a multilayer media dielectric resonator, a filter and other microwave devices, and has important industrial application values.

Description

A kind of low temperature sintering temperature-stable tungstate microwave dielectric ceramic

Technical field

The present invention relates to dielectric ceramic material, particularly relate to dielectric ceramic material of the microwave devices such as ceramic substrate, resonator and the wave filter used for the manufacture of microwave frequency and preparation method thereof.

Background technology

Microwave dielectric ceramic refers to and to be applied in microwave frequency band (mainly UHF and SHF frequency range) circuit as dielectric material and to complete the pottery of one or more functions, the components and parts such as resonator, wave filter, dielectric substrate and 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, telestar susceptor and 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 characteristics 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 low dielectric loss tan δ to reduce noise, general requirement Qf>=3000 GHz; (3) the temperature factor τ of resonant frequency _?little of as far as possible to ensure the thermostability that device has had, general requirement-10 ppm/DEG C≤τ _?≤+10 ppm/ DEG C.From late 1930s, just someone attempts dielectric substance to be applied to microwave technology in the world, and prepares TiO ₂microwave dielectric filter, but its temperature coefficient of resonance frequency τ _?too greatly cannot be practical.Since the seventies in last century, start the large-scale development to medium ceramic material, according to relative permittivity 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 _?≤ 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-factor, 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=20 ~ 35, 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 ~ 45, Q=(6 ~ 9) × 10 ³(under f=3 ~-4GHz), τ _?≤ 5 ppm/ ° C.Be mainly used in microwave military radar in 4 ~ 8 GHz range of frequency 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 range of frequency, 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 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 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 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, researchist 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 can low-temperature sintering have simultaneously near-zero resonance frequency temperature coefficient (-10 ppm/DEG C≤τ _?≤+10 ppm/ DEG C) be the emphasis of current research with the microwave dielectric ceramic of higher figure of merit.

Summary of the invention

The object of this invention is to provide and a kind of there is good thermostability and low-loss, simultaneously low temperature sintering microwave dielectric ceramic material and preparation method thereof.

The chemical constitution of microwave dielectric ceramic material of the present invention is: (1- x) Li ₂mg ₂w ₂o ₉+ xcaTiO ₃, wherein: 2%≤ x≤ 10%, x is molecular fraction.

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

(1) be 99.9%(weight percent by purity) more than Li ₂cO ₃, MgO, WO ₃, CaCO ₃, and TiO ₂starting powder by (1- x) Li ₂mg ₂w ₂o ₉+ xcaTiO ₃composition weigh batching, wherein 2%≤ x≤ 10%, x is molecular fraction.

(2) step (1) raw material wet ball-milling is mixed 12 hours, ball-milling medium is distilled water, pre-burning 6 hours in 820 DEG C of air atmosphere after oven dry.

(3) in the powder that step (2) is obtained, binding agent is added and after granulation, then compression moulding, finally in 870 ~ 920 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the polyvinyl alcohol solution of 5%, and polyvinyl alcohol addition accounts for 3% of powder total mass.

Advantage of the present invention: pottery of the present invention temperature can sinter below 950 DEG C, meet and burn requirement altogether with low cost silver electrode,: specific inductivity reaches 15 ~ 24, Qf value is up to 60000 ~ 78000GHz, temperature coefficient of resonance frequency is little, the manufacture of the microwave devices such as various medium substrate, resonator and wave filter can be widely used in, the technology needs of low temperature co-fired technology and microwave multilayer device can be met.

Embodiment

Embodiment:

Table 1 shows 4 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.

This pottery can be widely used in the manufacture of the microwave devices such as various medium substrate, resonator and wave filter, can meet the technology needs of the system such as mobile communication and satellite communications.

Table 1:

Claims (1)

1. a low temperature sintering temperature-stable microwave dielectric ceramic, is characterized in that the chemical constitution of described microwave dielectric ceramic is: (1- x) Li ₂mg ₂w ₂o ₉+ xcaTiO ₃, wherein: 2%≤ x≤ 10%, x is molecular fraction;

Preparation method's concrete steps of described microwave dielectric ceramic are:

(1) be 99.9%(weight percent by purity) more than Li ₂cO ₃, MgO, WO ₃, CaCO ₃, and TiO ₂starting powder by (1- x) Li ₂mg ₂w ₂o ₉+ xcaTiO ₃composition weigh batching, wherein 2%≤ x≤ 10%, x is molecular fraction;

(2) step (1) raw material wet ball-milling is mixed 12 hours, ball-milling medium is distilled water, pre-burning 6 hours in 820 DEG C of air atmosphere after oven dry;

(3) in the powder that step (2) is obtained, binding agent is added and after granulation, then compression moulding, finally in 870 ~ 920 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the polyvinyl alcohol solution of 5%, and polyvinyl alcohol addition accounts for 3% of powder total mass.