CN104045344A - Low temperature sinterable microwave dielectric ceramic Li2Zn3WO7 and preparation method thereof - Google Patents

Abstract

The invention discloses a low temperature sinterable microwave dielectric ceramic Li2Zn3WO7 and a preparation method thereof. The method includes: (1) conducting weighing and burdening on the original powder of Li2CO3, ZnO and WO3 with purity of more than 99.9% according to the composition of Li2Zn3WO7; (2) subjecting the raw materials obtained in step (1) to wet ball-milling mixing for 12h, taking distilled water as a milling medium, performing drying and then conducting presintering in a 700DEG C atmosphere for 6h; and (3) adding a binder into the powder prepared in step (2) and performing granulation, then conducting compression moulding, and finally carrying out sintering in a 750-780DEG C atmosphere for 4h. The binder is a polyvinyl alcohol solution with a mass concentration of 5%, and the adding amount of polyvinyl alcohol accounts for 3% of the total mass of the powder. The ceramic prepared by the invention can well sinter at 750-780DEG C, has a dielectric constant up to 15-16, a quality factor Qf value up to 69000-81000GHz, and a small temperature coefficient of resonant frequency, thus having substantial application value in industry.

Description

Can low-temperature sintered microwave dielectric ceramic Li 2zn 3wO 7and preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to the microwave devices such as medium substrate that use in microwave frequency, 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 and SHF frequency range) circuit as dielectric material and completes the pottery of one or more functions, in modern communication, be widely used as the components and parts such as resonator, wave filter, dielectric substrate and 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 and military radars, there is very important application, 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 to be applied to microwave technology in the world.

According to relative permittivity ε _rsize from use the different of frequency range, conventionally the microwave-medium ceramics being developed He 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 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 the GHz of f>=10), τ _?≈ 0.Be mainly used in the microwave communication equipments such as direct broadcasting satellite of f >=8 GHz as 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(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 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 these material systems is generally higher than 1300 ° of C above, can not be directly and the low melting point metal such as Ag and Cu burn altogether 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.

Explore with development of new can the process of low fired microwave dielectric ceramic materials in, 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 ₂moO ₄and Li ₂mTi ₃o ₈serial well behaved microwave-medium ceramics such as (M=Mg or Zn) etc., but microwave-medium ceramics system that can low fever is still more limited, and the τ of the low single-phase microwave dielectric ceramic of intrinsic sintering temperature _?conventionally larger, can not meet the requirement of device thermostability, this has limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.

We find Li ₂zn ₃wO ₇pottery has excellent comprehensive microwave dielectric property while sintering temperature lower than 800 °c, can be widely used in the manufacture of the microwave devices such as various medium substrates, can meet the Technology Need of low temperature co-fired technology and microwave multilayer device.

Summary of the invention

The object of this invention is to provide a kind of have low-loss and good thermostability, 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 Li ₂zn ₃wO ₇.

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

(1) by purity, be more than 99.9% Li ₂cO ₃, ZnO and WO ₃starting powder press Li ₂zn ₃wO ₇composition weigh batching.

(2) step (1) raw material wet ball-milling is mixed 12 hours, ball-milling medium is distilled water, pre-burning 6 hours in 700 ℃ of air atmosphere after oven dry.

(3) in the powder making in step (2), add after binding agent granulation, then compression moulding, finally sintering 4 hours in 750 ~ 780 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and polyvinyl alcohol addition accounts for 3% of powder total mass.

Useful technique effect of the present invention: ceramic sintering temperature is low, 750 ~ 780 ℃ of sintering are good; Its dielectric properties are excellent, and especially temperature coefficient of resonance frequency is closely zero, can meet the thermostability requirement of device; Quality factor q f value is up to 69000-81000GHz, industrial, has a great using value.

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 cylindrical dielectric resonator method.

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

Table 1:

Claims (1)

1. a low temperature sintering microwave dielectric ceramic, is characterized in that the chemical constitution of described microwave dielectric ceramic is: Li ₂zn ₃wO ₇;

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

(1) by purity, be more than 99.9% Li ₂cO ₃, ZnO and WO ₃starting powder press Li ₂zn ₃wO ₇composition weigh batching;

(2) step (1) raw material wet ball-milling is mixed 12 hours, ball-milling medium is distilled water, pre-burning 6 hours in 700 ℃ of air atmosphere after oven dry;

(3) in the powder making in step (2), add after binding agent granulation, then compression moulding, finally sintering 4 hours in 750 ~ 780 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and polyvinyl alcohol addition accounts for 3% of powder total mass.