CN103130496B

CN103130496B - Low-dielectric-constant microwave dielectric ceramic LiAlSi2O6 and preparation method thereof

Info

Publication number: CN103130496B
Application number: CN201310096891.0A
Authority: CN
Inventors: 方亮; 邓婧; 唐莹
Original assignee: Guilin University of Technology
Current assignee: Guangxi New Future Information Industry Co., Ltd.
Priority date: 2013-03-25
Filing date: 2013-03-25
Publication date: 2015-05-20
Anticipated expiration: 2033-03-25
Also published as: CN103130496A

Abstract

The invention discloses a low-dielectric-constant microwave dielectric ceramic LiAlSi2O6 and a preparation method thereof. The composition of the dielectric ceramic material is LiAlSi2O6. The preparation method comprises the following steps of: (1) mixing the original powder of Li2CO3, Al2O3 and SiO2 with the purity of above 99.9% based on the composition of LiAlSi2O6; (2) carrying out wet-type ball milling on the materials in step (1) for 12h, wherein the solvent is distilled water, and preburning for 12 hours in the atmosphere of 1000 DEG C subjected to drying; (3) adding an adhesive in the powder prepared in step (2), pelleting, and carrying out compression moulding, and finally sintering for 8 hours in the atmosphere of 1150-1180 DEG C, wherein the adhesive refers to polyvinyl alcohol solution with the mass concentration of 5% and accounts for 3% of the total amount of the powder. The prepared ceramic is sintered well at 1150-1180 DEG C, the dielectric constant reaches 5.1-5.3, the quality factor Qf is up to 101000-125000GHz, and the temperature coefficient of resonance frequency is low. The low-dielectric-constant microwave dielectric ceramic LiAlSi2O6 has great application value in the industry.

Description

Dielectric constant microwave dielectric ceramic LiAlSi 2o 6and preparation method thereof

Technical field

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

Background technology

Microwave dielectric ceramic refers to and to be applied in microwave frequency band (mainly UHF, 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 and 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 dielectric loss tan δ to reduce noise, general requirement Qf>=3000 GHz; (3) the temperature factor t of resonant frequency _flittle of as far as possible to ensure the thermostability that device has had, 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 e _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 _?≤ 5 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=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, mainly with BaTi ₄o ₉, Ba ₂ti ₉o ₂₀(Zr, Sn) TiO ₄deng the MWDC material for 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 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, 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 fired microwave dielectric ceramic material be the emphasis of current research without 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, wherein a large amount of exploratory developments concentrates on Li base binary or ternary compound, and have developed as Li ₂tiO ₃, Li ₃nbO ₄, Li ₂moO ₄, Li ₂mTi ₃o ₈(M=Mg, Zn) and Li ₂mgSiO ₄etc. serial microwave-medium ceramics of good performance, but the system of the low dielectric constant microwave ceramic medium of sintering temperature is still more limited, which greatly limits the development of low temperature co-fired technology and microwave multilayer device.Document [G ü nther J. Redhammer, Georg Roth, Structural variation and crystal chemistry of LiMe ³⁺si ₂o ₆clinopyroxenes Me ³⁺=Al, Ga, Cr, V, Fe, Sc and In. Zeitschrift f ü r Kristallographie-Crystalline Materials:2004,219 (5): 278-294] report triphane LiAlSi ₂o ₆crystalline structure, consider and yet there are no about triphane LiAlSi ₂o ₆ceramic preparation and the research of microwave dielectric property report, we are to LiAlSi ₂o ₆pottery has carried out sintering characteristic and Study on microwave dielectric property, found that this pottery have excellent comprehensive microwave dielectric property simultaneously sintering temperature lower than 1200 °c, can be widely used in the manufacture of the microwave devices such as various medium substrate, resonator and wave filter.

Summary of the invention

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

Dielectric ceramic material of the present invention consist of LiAlSi ₂o ₆.

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

(1) be the Li of more than 99.9% by purity ₂cO ₃, Al ₂o ₃and SiO ₂starting powder press LiAlSi ₂o ₆composition batching.

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 12 hours in 1000 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 1150 ~ 1180 DEG C of air atmosphere, sinter 8 hours; Described binding agent adopts mass concentration to be the polyvinyl alcohol solution of 5%, and dosage accounts for 3% of powder total amount.

Pottery prepared by the present invention is good at 1150 ~ 1180 DEG C of sintering, and its specific inductivity reaches 5.1 ~ 5.3, and quality factor q f value is up to 101000-125000 GHz, and temperature coefficient of resonance frequency is little, industrially has 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, satellite communications.

The present invention is never limited to above embodiment, have with the element of Al analog structure and chemical property as Fe, V, Gd, In and Cr etc. also can make with analogous crystalline structure of the present invention and performance dielectric ceramic.

Claims

1. lithium base composite oxidate is as an application for dielectric constant microwave dielectric ceramic, it is characterized in that consisting of of described lithium base composite oxidate: LiAlSi ₂o ₆;

Preparation method's step of described lithium base composite oxidate is:

(1) be the Li of more than 99.9% by purity ₂cO ₃, Al ₂o ₃and SiO ₂starting powder press LiAlSi ₂o ₆composition batching;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 12 hours in 1000 DEG C of air atmosphere after oven dry;