CN103204680B - Niobate microwave dielectric ceramic LiMNb3O9 and preparation method thereof - Google Patents

Abstract

The invention discloses a niobate microwave dielectric ceramic LiMNb3O9 and a preparation method thereof. The niobate microwave dielectric ceramic material is constituted by LiMNb3O9, wherein M is one of Zn, Mg and Ni. The preparation method comprises the steps of: (1) weighing and mixing the raw powder of Li2CO3, MO and Nb2O5 with the purity over 99.9% according to the LiMNb3O9 chemical formula, wherein the M is one of Zn, Mg and Ni; (2) mixing the raw materials in the step (1) by wet-type ball milling for 12 hours with distilled water as the solvent, and an obtained mixture is dried and then pre-burned at 1000 DEG C for 6 hours; and (3) adding a binder into the powder prepared in the step (2) for pelleting, molding by pressing and finally sintering the molded product at 1050-1100 DEG C for 4 hours, wherein a polyvinyl alcohol solution with the mass concentration being 5% is employed as the binder and the the binder accounts for 3% of the total powder. The ceramic prepared according to the invention is well sintered at 1050-1100 DEG C, has a dielectric constant being 37-41, a quality factor Qf as high as 55000-82000GHz, a small temperature coefficient of resonance frequency and has great value in industry application.

Description

Columbate microeave dielectric ceramic LiMNb 3o 9and 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 resonator and 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, 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, 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, telstar recipient 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 property: (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 Requirements Qf>=3000 GHz; (3) the temperature coefficient τ of resonance frequency _?the as far as possible little thermal stability to ensure that device has had, General Requirements-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 dielectric constant 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 hybrid 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 frequency ranges 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 frequency range, 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, Pr etc., abbreviation 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 ₃dielectric constant 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 multilayer 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, researcher 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, tungstates architecture compound and tellurate architecture compound that intrinsic sintering temperature is low get the attention and study, wherein a large amount of exploratory developments concentrates on Li base binary or ternary compound, and has developed as Li ₂tiO ₃, Li ₃nbO ₄, Li ₂moO ₄and Li ₂mTi ₃o ₈serial well behaved microwave-medium ceramics such as (M=Mg, Zn) etc., still, can low fever's microwave-medium ceramics system still more limited, this have limited the development of low temperature co-fired technology and microwave multilayer device to a great extent.We are to the serial niobates LiMNb containing lithium ₃o ₉(M=Zn, Mg and Ni) pottery has carried out sintering characteristic and Study on microwave dielectric property, found that this pottery has excellent comprehensive microwave dielectric property while sintering temperature lower than 1150 °c, can be widely used in the manufacture of the microwave devices such as various resonators and filter.

Summary of the invention

The object of this invention is to provide a kind of have low-loss and good thermal stability, microwave dielectric ceramic material that sintering temperature is lower simultaneously and preparation method thereof.

Microwave dielectric ceramic material of the present invention consist of LiMNb ₃o ₉, wherein M is the one in Zn, Mg and Ni;

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

(1) be more than 99.9% Li by purity ₂cO ₃, MO and Nb ₂o ₅starting powder press LiMNb ₃o ₉chemical formula weigh batching, wherein M is the one in Zn, Mg and Ni.

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 1000 DEG C of air atmosphere after oven dry.

(3) in the powder making in step (2), add after binding agent granulation, more compressing, finally sintering 4 hours in 1050 ~ 1100 DEG C of air atmosphere; Described binding agent adopts the poly-vinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total amount.

Pottery prepared by the present invention is good at 1050-1100 DEG C of sintering, and its dielectric constant reaches 37～41, and quality factor q f value is up to 55000-82000GHz, and temperature coefficient of resonance frequency is little, has a great using value industrial.

Embodiment

Embodiment:

Table 1 shows 6 specific embodiments and the microwave dielectric property thereof that form different composition of the present invention and sintering temperature.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 various medium substrates, resonance plays the manufacture of the microwave device such as device, filter, can meet the Technology Need of the system such as mobile communication, satellite communication.

Table 1:

Claims (1)

1. niobates, as an application for microwave dielectric ceramic, is characterized in that the chemical composition general formula of described niobates is: LiMNb ₃o ₉, wherein M is the one in Mg and Ni;

Preparation method's step of described niobates is:

(1) be more than 99.9% Li by purity ₂cO ₃, MO and Nb ₂o ₅starting powder press LiMNb ₃o ₉chemical formula weigh batching, wherein M is the one in Mg and Ni;

(2) step (1) raw material wet ball-milling is mixed 12 hours, solvent is distilled water, pre-burning 6 hours in 1000 DEG C of air atmosphere after oven dry;

(3) in the powder making in step (2), add after binding agent granulation, more compressing, finally sintering 4 hours in 1050 ~ 1100 DEG C of air atmosphere; Described binding agent adopts the poly-vinyl alcohol solution that mass concentration is 5%, and dosage accounts for 3% of powder total amount.