CN104725044A - Temperature-stable microwave dielectric ceramic LiMg2V7O20 with ultra-low dielectric constant - Google Patents

Abstract

The invention discloses temperature-stable microwave dielectric ceramic LiMg2V7O20 with an ultra-low dielectric constant and a preparation method of the ceramic LiMg2V7O20. The preparation method comprises the following steps: (1) weighing and proportioning Li2CO3, MgO and V2O5 original powder which have purities of 99.9wt% or above; (2) carrying out wet ball-milling mixing on the raw material obtained in the step (1) for 12h, drying and then presintering in a 750 DEG C air atmosphere for 6h, wherein the ball milling medium is distilled water; and (3) adding a binder to the powder obtained in the step (2), granulating, carrying out compression moulding, and finally sintering for 4h in a 800-850 DEG C air atmosphere, wherein the binder is a polyvinyl alcohol solution with a mass concentration of 5% and the addition amount of polyvinyl alcohol accounts for 3% of the total mass of the powder. The prepared ceramic has good sintering performance at a temperature of 850 DEG C or below; the dielectric constant reaches 16.4-17.3, the quality factor (QF) value is high up to 97000-143000GHz, and the temperature coefficient of resonance frequency is small, and thus the temperature-stable microwave dielectric ceramic LiMg2V7O20 with an ultra-low dielectric constant has extremely large industrial application value.

Description

Temperature-stable ultralow dielectric microwave dielectric ceramic LiMg 2v 7o 20

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, resonator is widely used as in modern communication, wave filter, the components and parts such as dielectric substrate and medium wave circuit, it is the key foundation material of modern communication technology, at portable mobile phone, automobile telephone, cordless telephone, there is very important application the aspects such as telestar susceptor and military radar, in the miniaturization of modern communication instrument, increasing effect is just being played in integrated process.

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>=3000GHz; (3) the temperature factor τ of resonant frequency _flittle of as far as possible to ensure the thermostability that device has had, general requirement-10ppm/ DEG C≤τ _f≤+10ppm/ 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 _ftoo 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 _f≤ 10ppm/ DEG 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 f>=10GHz), τ _f≈ 0.Be mainly used in the microwave communication equipments such as the direct broadcasting satellite of f >=8GHz 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 _f≤ 5ppm/ DEG C.Be mainly used in microwave military radar in 4 ~ 8GHz 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 DEG 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 (LowTemperature 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 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 research, but due to three performance index (ε of microwave dielectric ceramic _rwith Qf and τ _f) 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 and low-temperature sintering can have near-zero resonance frequency temperature coefficient (-10ppm/ DEG C≤τ with exploitation simultaneously _f≤+10ppm/ 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 composition LiMg ₂v ₇o ₂₀, LiCu ₂v ₇o ₂₀, LiNi ₂v ₇o ₂₀series compound carried out the research of microwave dielectric property, find that their sintering temperature is lower than 900 DEG C, but only have LiMg ₂v ₇o ₂₀there is near-zero resonance frequency temperature coefficient and high quality factor, LiNi ₂v ₇o ₂₀the temperature coefficient of resonance frequency τ of pottery _f(being respectively-91ppm/ DEG C) bigger than normal and dielectric loss is also higher and cannot as microwave-medium ceramics that can be practical.LiCu ₂v ₇o ₂₀for ionophore does not have resonance peak at microwave frequency band.

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 ultralow dielectric microwave dielectric ceramic material and preparation method thereof.

The chemical constitution of microwave dielectric ceramic material of the present invention is LiMg ₂v ₇o ₂₀.

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

(1) by purity be the Li of more than 99.9% (weight percent) ₂cO ₃, MgO and V ₂o ₅starting powder press LiMg ₂v ₇o ₂₀composition 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 750 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 800 ~ 850 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: LiMg ₂v ₇o ₂₀ceramic sintering temperature is low, and raw materials cost is low; Specific inductivity reaches 16.4 ~ 17.3, the temperature factor τ of its resonant frequency _flittle, temperature stability is good; Quality factor q f value, up to 97000-143000GHz, 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.

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. a temperature-stable ultralow dielectric microwave dielectric ceramic, is characterized in that the chemical constitution of described microwave dielectric ceramic is: LiMg ₂v ₇o ₂₀;

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 and V ₂o ₅starting powder press LiMg ₂v ₇o ₂₀composition 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 750 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 800 ~ 850 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.