CN104628384A - Low-loss temperature-stable type middle-dielectric-constant microwave dielectric ceramic LiBi2NbO6 - Google Patents

Abstract

The invention discloses a composite oxide LiBi2NbO6 which can be applied as a temperature-stable type middle-dielectric-constant microwave dielectric ceramic capable of being sintered at low temperature and a preparation method of the composite oxide LiBi2NbO6. The preparation method comprises the following steps: (1) weighing and batching original powder of Li2CO3, Bi2O3 and Nb2O5 with the purity of more than 99.9% (in percentage by weight) according to the composition of LiBi2NbO6; (2) performing wet ball milling and mixing on raw materials in the step (1) for 12 hours by taking absolute ethyl alcohol as a ball milling medium, and pre-burning for 6 hours at an air atmosphere at 850 DEG C after drying; and (3) adding an adhesion agent into powder prepared in the step (2), granulating, then performing compression molding, and finally sintering for 4 hours at the air atmosphere at 900-950 DEG C, wherein the adhesion agent adopts a polyvinyl alcohol solution with the mass concentration of 5%, and the addition quantity of polyvinyl alcohol accounts for 3% of the total mass of the powder. The prepared ceramic disclosed by the invention is good in sintering, ensures that the dielectric constant can reach 37.3 to 38.7 and a quality factor (Qf) value can reach 64000-79000GHz, is small in temperature coefficient of resonance frequency, and has great application values in industry.

Description

Low-loss temperature-stabilized medium dielectric constant microwave medium microwave dielectric ceramic LiBi 2nbO 6

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 is the emphasis of current research without the low fired microwave dielectric ceramic material of glassy phase.

Can in the process of low fired microwave dielectric ceramic materials in exploration and development of new, the material system that intrinsic sintering temperature is low gets the attention and research, but due to three performance index (ε of microwave dielectric ceramic _rwith Qf and τ _?) between be that the relation of mutually restriction is (see document: the restricting relation between microwave dielectric ceramic materials dielectric properties, Zhu Jianhua, Liang Fei, Wang little Hong, Lv Wenzhong, electronic component and material, phase March the 3rd in 2005), meet three performance requriementss and the single-phase microwave-medium ceramics of low temperature sintering is considerably less, mainly their temperature coefficient of resonance frequency is usually excessive or quality factor are on the low side and cannot application request.Current is the summary of experience drawn by great many of experiments to the research major part of microwave-medium ceramics, but complete theory is not had to set forth the relation of microtexture and dielectric properties, therefore, in theory also cannot predict its microwave dielectric property such as temperature coefficient of resonance frequency and quality factor from the composition of compound and structure, which greatly limits the development of low temperature co-fired technology and microwave multilayer device.Explore with exploitation can low-temperature sintering have simultaneously near-zero resonance frequency temperature coefficient (-10 ppm/DEG C≤τ _?≤+10 ppm/ DEG C) be that those skilled in the art thirst for solving always but are difficult to the difficult problem that succeeds all the time with the microwave dielectric ceramic of higher figure of merit.

We are to consisting of LiBi ₂nbO ₆, LiLa ₂nbO ₆, LiNd ₂nbO ₆and LiBi ₂sbO ₆series compound carried out the research of microwave dielectric property, find that their sintering temperature is lower than 1200 DEG C, but only have LiBi ₂nbO ₆there is near-zero resonance frequency temperature coefficient and high quality factor, LiBi ₂sbO ₆the temperature coefficient of resonance frequency τ of pottery _?(being respectively-91 ppm/ DEG C) bigger than normal and dielectric loss is also higher and cannot as microwave-medium ceramics that can be practical.LiLa ₂nbO ₆and LiNd ₂nbO ₆for semi-conductor does not have resonance peak at microwave frequency band.

Summary of the invention

The object of this invention is to provide one can low-temperature sintering and have good thermal stability and low-loss medium dielectric constant microwave medium microwave dielectric ceramic material and preparation method thereof.

The chemical constitution of microwave dielectric ceramic material of the present invention is LiBi ₂nbO ₆.

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

(1) be 99.9%(weight percent by purity) more than Li ₂cO ₃, Bi ₂o ₃and Nb ₂o ₅starting powder press LiBi ₂nbO ₆composition weigh batching.

(2) step (1) raw material wet ball-milling is mixed 12 hours, ball-milling medium is dehydrated alcohol, pre-burning 6 hours in 850 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 900 ~ 950 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the polyvinyl alcohol solution of 5%, and the addition of polyvinyl alcohol accounts for 3% of powder total mass.

Advantage of the present invention: LiBi ₂nbO ₆pottery sintering below 960 DEG C is good, and specific inductivity reaches 37.3 ~ 38.7, especially the temperature factor τ of resonant frequency _?little, temperature stability is good; Quality factor q f value, up to 64000-79000GHz, 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 low temperature co-fired technology and microwave multilayer device, industrially have great using value.

Embodiment

Embodiment:

Table 1 shows 3 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., as composite oxides for temperature-stable medium dielectric constant microwave medium microwave dielectric ceramic application, it is characterized in that the chemical constitution of described composite oxides is: LiBi ₂nbO ₆;

Preparation method's step of described composite oxides is:

(1) be 99.9%(weight percent by purity) more than Li ₂cO ₃, Bi ₂o ₃and Nb ₂o ₅starting powder press LiBi ₂nbO ₆composition 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 850 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 900 ~ 950 DEG C of air atmosphere, sinter 4 hours; Described binding agent adopts mass concentration to be the polyvinyl alcohol solution of 5%, and the addition of polyvinyl alcohol accounts for 3% of powder total mass.