CN103539444A - Low temperature sintering microwave dielectric ceramic Ca2Bi2O5 and preparation method thereof - Google Patents

Abstract

The invention discloses low temperature sintering microwave dielectric ceramic Ca2Bi2O5 and a preparation method thereof. Composition of the low temperature sintering microwave dielectric ceramic is Ca2Bi2O5. The preparation method comprises the following steps: (1) weighing and dosing original powder of CaCO3 and Bi2O3 with the purity over 99.9% according to the chemical formula Ca2Bi2O5; (2) wet-type ball-milling and mixing the raw material in step (1) for 12 hours, wherein the solvent is distilled water, and drying and pre-sintering for 6 hours in atmosphere at 750 DEG C; and (3) adding a binder into the powder prepared in step (2) and prilling, then, pressing to mould, and finally, sintering for 4 hours in atmosphere at 820-850 DEG C, wherein the binder is polyvinyl alcohol liquor with mass concentration of 5%, and the dose accounts for 3% of total weight of the powder. The ceramic disclosed by the invention is well sintered at 820-850 DEG C, and the dielectric constant reaches 1-20, the quality factor Qf value reaches 62000-89000GHz and the temperature coefficient of resonance frequency is small. The ceramic has an extremely huge application value in industry.

Description

Low-temperature sintered microwave dielectric ceramic Ca 2bi 2o 5and preparation method thereof

Technical field

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

Background technology

Microwave dielectric ceramic refers to and is applied in microwave frequency band (being mainly UHF, 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 dielectric ceramic 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, low temperature sintering high performance microwave media ceramic system is still very limited at present, and this has limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.

Summary of the invention

The object of this invention is to provide a kind of have low-loss and good temperature stability, high-frequency dielectric constant reaches 19 ~ 20, Qf value up to 62000-89000GHz simultaneously, can be at microwave dielectric ceramic of 820-850 ℃ of sintering and preparation method thereof.

The chemical constitution formula of microwave dielectric ceramic of the present invention is: Ca ₂bi ₂o ₅.

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

(1) by purity, be more than 99.9% CaCO ₃and Bi ₂o ₃starting powder press Ca ₂bi ₂o ₅chemical formula weigh batching.

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 750 ℃ 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 820 ~ 850 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total mass.

Therefore pottery prepared by the present invention is good at 720-750 ℃ of sintering, and its specific inductivity reaches 19～20, and quality factor q f value is up to 62000 ~ 89000GHz, and temperature coefficient of resonance frequency is little, has a great using value industrial.

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.

The present invention is never limited to above embodiment.The bound of sintering temperature, interval value can realize the present invention, at this, do not enumerate embodiment.

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 systems such as mobile communication, satellite communications.

Table 1:

Claims (1)

1. composite oxides are as an application for low-temperature sintered microwave dielectric ceramic, and the chemical constitution formula that it is characterized in that described composite oxides is Ca ₂bi ₂o ₅:

Preparation method's concrete steps of described composite oxides are:

(1) by purity, be more than 99.9% CaCO ₃and Bi ₂o ₃starting powder press Ca ₂bi ₂o ₅chemical formula weigh batching;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 750 ℃ 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 820 ~ 850 ℃ of air atmosphere; Described binding agent adopts the polyvinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total mass.