CN100386285C

CN100386285C - Low temp. sintering niobate microwave dielectric ceramic and preparation process thereof

Info

Publication number: CN100386285C
Application number: CNB2006100181125A
Authority: CN
Inventors: 方亮; 张辉; 孟森森
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2006-01-05
Filing date: 2006-01-05
Publication date: 2008-05-07
Anticipated expiration: 2026-01-05
Also published as: CN1793004A

Abstract

The present invention discloses low-temperature sintered high-frequency niobate dielectric ceramic which is used for microwave components and microwave ceramic capacitors or temperature compensation capacitors. The ceramic takes (Ba<1-x>Sr<x>) 4LiNb<3-y>Ta<y>O12 as the basic phase, wherein 0.00<=x<=1 and 0.00<=y<=2. By adopting a corresponding method to prepare the ceramic, the ceramic is well sintered, the high-frequency dielectric constant reaches 40 to 90, and the ceramic has low consumption, small temperature coefficient of resonance frequency and great application value in industry.

Description

Low-temperature sintering columbate microeave dielectric ceramic and preparation method thereof

Technical field

The present invention relates to dielectric ceramic material, particularly relate to microwave devices such as the dielectric resonator that uses in microwave frequency, wave filter, and the dielectric ceramic material of ceramic condenser or thermo-compensation capacitor and preparation method thereof.

Background technology

Microwave dielectric ceramic is meant and is applied in microwave frequency band (mainly being UHF, the SHF frequency range) circuit as dielectric material and finishes the pottery of one or more functions, in modern communication, be widely used as components and parts such as resonator, wave filter, dielectric substrate, 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, military radars crucial application is arranged, 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 satisfy the requirement of following dielectric characteristics: the relative permittivity ε that (1) is high _rBe beneficial to miniaturization of devices, general requirement ε _r〉=20; (2) high quality factor q value or dielectric loss tan δ are to reduce noise, general requirement Qf 〉=3000; (3) the temperature factor τ of resonant frequency _fAs far as possible little of guaranteeing that device has good thermostability, general requirement-10/ ℃≤τ _f≤+10ppm/ ℃.In the world from late 1930s just the someone attempt dielectric substance is applied to microwave technology.

According to relative permittivity ε _rSize with use the different of frequency range, the microwave-medium ceramics that is developed He developing can be divided into 3 classes usually.

(1) low ε _rWith the microwave dielectric ceramic of high Q value, mainly be 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=(1～3) * 10 ⁴(under f 〉=10GHz), τ _f≈ 0.Be mainly used in the microwave communication equipments such as direct broadcasting satellite of f 〉=8GHz as the dielectric resonance device.

(2) medium ε _rWith the microwave dielectric ceramic of Q value, mainly be 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 _f≤ 5ppm/ ℃.Be mainly used in interior microwave military radar of 4～8GHz range of frequency and the communication system as the dielectric resonance device.

(3) 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, and this also is the emphasis of microwave dielectric ceramic research.Since the eighties, physiognomy secondary such as Kolar, Kato are existing and studied perovskite-like tungsten bronze type BaO-Ln 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 ₃Specific inductivity reaches 105).

Accelerated development along with information technology, mobile communication system develops to high frequencyization, miniaturization, integrated, high reliability direction, medium dielectric constant material system specific inductivity is on the low side, is difficult to satisfy the demand of further miniaturization under the prerequisite that keeps the Q value not reduce.And the high dielectric constant material system mainly is that over-all properties is relatively poor, and the Qf value is less, is difficult to satisfy the growth requirement of high frequencyization, high reliability.The sintering temperature of these material systems generally is higher than 1300 ℃ in addition, can not be directly and low melting point metals such as Ag, Cu burn the formation laminated ceramic capacitor altogether.

Summary of the invention

The purpose of this invention is to provide a class and have low-loss and good thermostability, have the high-frequency dielectric constant simultaneously and reach 40～90, can be at 1300 ℃ of following agglomerating dielectric ceramic materials and preparation method thereof.

Dielectric ceramic material of the present invention is made up of Ba, Sr, Li, Nb and the Ta by oxide form, and is principal phase with the crystalline phase of following composition,

(Ba _1-xSr _x) ₄LiNb _3-yTa _yO ₁₂

In the formula, 0.00≤x≤1,0.00≤y≤2.

This dielectric ceramic material is prepared from as follows.

Method one: at first be the BaCO more than 99.9% with purity ₃, SrCO ₃, Li ₂CO ₃, Nb ₂O ₅With Ta ₂O ₅Starting powder by batching in the described compositing range, wet ball-milling mixed 12～24 hours, solvent is a distilled water, the pre-burning 4～8 hours in 900～1250 ℃ of air atmosphere of oven dry back, after in preburning powder, adding binding agent and granulation then, compression moulding again, sintering 1～8 hour in 950～1300 ℃ of air atmosphere at last, described binding agent employing mass concentration is 5% polyvinyl alcohol water solution, and dosage accounts for 5%～15% of powder total mass.

Method two: at first be the Li more than 99.9% with purity ₂CO ₃With Nb ₂O ₅Starting powder by molecular ratio 1～1.05: 2 mixes, wet ball-milling mixed 12～24 hours, solvent is a distilled water, the oven dry back in 1000～1150 ℃ of air atmosphere pre-burning 4～8 hours with synthetic LiNbO ₃, be the BaCO more than 99.9% then with purity ₃, SrCO ₃, Nb ₂O ₅And Ta ₂O ₅Starting powder and synthetic LiNbO ₃By batching in the described compositing range, wet ball-milling mixed 12～24 hours, solvent is a distilled water, calcined 4～8 hours in 900～1250 ℃ of air atmosphere the oven dry back, after in calcined powder, adding binding agent and granulation then, compression moulding again, sintering more than 1 hour in 950～1300 ℃ of air atmosphere at last, described binding agent employing mass concentration is 5% polyvinyl alcohol water solution, and dosage is 5%～15% of powder total mass.

This dielectric ceramic material or be added with parafacies, the purpose that adds parafacies are in order to adjust sintering temperature, and parafacies is low-melting oxide compound V ₂O ₅, CuO and MnO a kind of or their mixture, incorporation accounts for 0.25%～5% of powder total mass; Or parafacies is B ₂O ₃, incorporation accounts for 5%～25% of powder total mass.

This dielectric ceramic material has the preparation method of principal phase and parafacies, make earlier pre-burning principal phase powder as stated above, the purity of contained element is the oxide powder more than 99.9% in then pre-burning principal phase powder and parafacies being formed, mixed 12～24 hours by the weight percent wet ball-milling of setting, solvent is a distilled water, binding agent and granulation are added in the oven dry back, compression moulding again, sintering more than 1 hour in 950～1300 ℃ of air atmosphere at last, described binding agent employing mass concentration is 5% polyvinyl alcohol water solution, and dosage is 1%～15% of powder total mass.Binding agent or employing polyglycol solution.

Description of drawings

Fig. 1 consists of Ba ₄LiNb ₃O ₁₂X-ray diffractogram

Embodiment

Table 1 shows several specific exampless and the microwave dielectric property thereof that constitutes each component content of the present invention.Its preparation method carries out material phase analysis with the ceramic sample of powder X-ray diffractometry after to sintering as mentioned above, and Fig. 1 is the X ray diffracting spectrum of embodiment 1, carries out the evaluation of microwave dielectric property with the cylindrical dielectric resonator method.

This pottery can be widely used in the manufacturing of microwave devices such as various dielectric resonators, wave filter, can satisfy the Technology Need of systems such as mobile communication, satellite communications.

With the Elements C a of Ba, Sr analog structure and chemical property, Pb etc., with the element ti of Nb analog structure and chemical property, Sn, Zr etc. also can make the dielectric ceramic with analogous crystalline structure of the present invention and performance.

[table 1]

x	y	Molecular formula	Sintering temperature	ε _r	Qf (GHz)	τ _f (ppm/℃)
x	y	Molecular formula	Sintering temperature	ε _r	Qf (GHz)	τ _f (ppm/℃)	0	0	Ba ₄LiNb ₃O ₁₂	950	90	13000	15
0.25	0.5	Ba ₃SrLiNb _2.5Ta _0.5O ₁₂	1100	70	23000	2	0	0	Ba ₄LiNb ₃O ₁₂	950	90	13000	15
0.25	0.5	Ba ₃SrLiNb _2.5Ta _0.5O ₁₂	1100	70	23000	2	0.5	1	Ba ₂Sr ₂LiNb ₂TaO ₁₂	1200	58	24000	-8
0.75	2	BaSr ₃LiNbTa ₂O ₁₂	1250	48	27000	-16	0.5	1	Ba ₂Sr ₂LiNb ₂TaO ₁₂	1200	58	24000	-8
0.75	2	BaSr ₃LiNbTa ₂O ₁₂	1250	48	27000	-16	1	2	Sr ₄LiNbTa ₂O ₁₂	1300	40	15000	-30

Claims

1. low-temperature sintering columbate microeave dielectric ceramic is made up of the oxide compound of the Nb of the Li of the Ba of oxide form and/or Sr, oxide form, oxide form, optional Ta, and is principal phase with the crystalline phase of following composition,

(Ba _1-xSr _x) ₄LiNb _3-yTa _yO

In the formula, 0.00≤x≤1 0.00≤y≤2.

2. the preparation method of the described low-temperature sintering columbate microeave dielectric ceramic of claim 1 is characterized in that: at first, be BaCO more than 99.9% with purity ₃Or/and SrCO ₃, Li ₂CO ₃, Nb ₂O ₅With optional Ta ₂O ₅Starting powder by batching in the described crystalline phase compositing range of claim 1, wet ball-milling mixed 12～24 hours, solvent is a distilled water, the pre-burning 4～8 hours in 900～1250 ℃ of air atmosphere of oven dry back, after in preburning powder, adding binding agent and granulation then, compression moulding again, sintering more than 1 hour in 950～1300 ℃ of air atmosphere at last, described binding agent employing mass concentration is 5% polyvinyl alcohol water solution, and dosage is 5%～15% of powder total mass.

3. the preparation method of the described low-temperature sintering columbate microeave dielectric ceramic of claim 1 is characterized in that: at first, be Li more than 99.9% with purity ₂CO ₃With Nb ₂O ₅Starting powder by molecular ratio 1～1.05: 2 mixes, wet ball-milling mixed 12～24 hours, solvent is a distilled water, the oven dry back in 1000～1150 ℃ of air atmosphere pre-burning 4～8 hours with synthetic LiNbO ₃, be the BaCO more than 99.9% then with purity ₃Or/and SrCO ₃, Nb ₂O ₅With optional Ta ₂O ₅Starting powder and synthetic LiNbO ₃By batching in the described crystalline phase compositing range of claim 1, wet ball-milling mixed 12～24 hours, solvent is a distilled water, calcined 4～8 hours in 900～1250 ℃ of air atmosphere the oven dry back, after in calcined powder, adding binding agent and granulation then, compression moulding again, sintering more than 1 hour in 950～1300 ℃ of air atmosphere at last, described binding agent employing mass concentration is 5% polyvinyl alcohol water solution, and dosage is 5%～15% of powder total mass.