CN104003723A - Microwave dielectric ceramic Li3Zn4NbO8 capable of realizing low-temperature sintering and preparation method thereof - Google Patents

Abstract

The invention discloses a temperature-stable microwave dielectric ceramic Li3Zn4NbO8 capable of realizing low-temperature sintering. The preparation method comprises the following specific steps: (1) performing weigh batching on original powder of Li2CO3, ZnO and Nb2O5 of which the purity is above 99.9% according to the chemical formula of Li3Zn4NbO8; (2) performing wet ball milling and mixing on the raw materials in the step (1) for 12 hours by using distilled water as a ball milling medium, drying, and then presintering in the atmospheric atmosphere at 800 DEG C for 6 hours; and (3) adding an adhesive into the powder prepared in the step (2), granulating, performing compression molding, and finally sintering in the atmospheric atmosphere at 850-900 DEG C for 4 hours, wherein the adhesive is a polyvinyl alcohol solution of which the mass concentration is 5%, and the addition amount of the polyvinyl alcohol accounts for 3% of the total mass of the powder. For the ceramic prepared by the invention, the sintering temperature is low, the temperature coefficient of resonance frequency is small, the temperature stability is favorable, the dielectric constant reaches 26-27, and the quality factor Qf value is up to 71000-87000 GHz. Thus, the ceramic has great industrial application value.

Description

Low temperature sintering microwave dielectric ceramic Li 3zn 4nbO 8and preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to dielectric ceramic material of the microwave device such as medium substrate, resonator and wave filter using in microwave frequency 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, there is very important application at aspects such as portable mobile phone, automobile telephone, cordless telephone, telestar susceptor and military radars, 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 thermostability to ensure that device has had close to zero as far as possible, general requirement-10/ DEG C≤τ _?≤+10 ppm/ DEG C.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 frequency range different, conventionally the microwave-medium ceramics being 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 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 the 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 developing without the low fired microwave dielectric ceramic material of glassy phase is the emphasis of current research.

Explore with development of new can the process of low fired microwave dielectric ceramic materials in, the material systems such as Li based compound, Bi based compound, tungstate architecture compound and tellurate architecture compound that intrinsic sintering temperature is low get the attention and study, but the subject matter existing is, the temperature coefficient of resonance frequency of the single-phase microwave dielectric ceramic material of low temperature sintering of most open reports is all bigger than normal, cannot ensure the thermostability that device has had; And up to now by existing theory or the also τ of unpredictable monophase materials of technology _?value, 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 ₃zn ₄nbO ₈new compound carried out sintering characteristic and Study on microwave dielectric property, found that such pottery have excellent comprehensive microwave dielectric property simultaneously sintering temperature lower than 900 °c, can realize low temperature co-fired with Ag, can be widely used in the manufacture of the microwave devices such as various medium substrates, resonator and wave filter, can meet the needs 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 Heat stability is good and low-loss, and can low sintering microwave dielectric ceramic material and preparation method thereof.

The chemical constitution formula of microwave dielectric ceramic material of the present invention is Li ₃zn ₄nbO ₈.

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

(1) be more than 99.9% Li by purity ₂cO ₃, ZnO and Nb ₂o ₅starting powder press Li ₃zn ₄nbO ₈chemical formula 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 800 DEG C 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 850 ~ 900 DEG C of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and the addition of polyvinyl alcohol accounts for 3% of powder total mass.

Of the present invention useful technique effectbe: the claimed ceramic sintering temperature of the present invention is low, can meet the Technology Need of low temperature co-fired technology and microwave multilayer device; The temperature factor τ of its resonant frequency _?close to zero, can meet the heat-staple requirement of device; Specific inductivity reaches 26～27, and quality factor q f value, up to 71000-87000GHz, can be widely used in the manufacture of the microwave devices such as various medium substrates, resonator and wave filter, has a great using value industrial.

Embodiment

Embodiment:

Table 1 shows 3 specific embodiments and the microwave dielectric property thereof that form different sintering temperatures of the present invention.Its preparation method is described above, carries out the evaluation of microwave dielectric property by cylindrical dielectric resonator method.Just Li ₃zn ₄nbO ₈powder mixes with the Ag powder that accounts for powder quality 20%, after compression moulding, sintering 4 hours at 900 DEG C;

X ray diffraction material phase analysis and scanning electron microscopic observation all show Li ₃zn ₄nbO ₈there is not chemical reaction, i.e. Li with Ag ₃zn ₄nbO ₈can be low temperature co-fired with Ag electrode.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 system 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 formula of described microwave dielectric ceramic is: Li ₃zn ₄nbO ₈;

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

(1) be more than 99.9% Li by purity ₂cO ₃, ZnO and Nb ₂o ₅starting powder press Li ₃zn ₄nbO ₈chemical formula 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 800 DEG C 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 850 ~ 900 DEG C of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and the addition of polyvinyl alcohol accounts for 3% of powder total mass.