CN1204084C

CN1204084C - Preparation method of constant thermal expansion lead strontium titanate positive resistance temperature coefficient ceramics

Info

Publication number: CN1204084C
Application number: CN 03100012
Authority: CN
Inventors: 邢献然; 陈骏; 邓金侠; 刘桂荣
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2003-01-03
Filing date: 2003-01-03
Publication date: 2005-06-01
Anticipated expiration: 2023-01-03
Also published as: CN1443725A

Abstract

The present invention relates to a method for preparing ferroelectric functional ceramic materials, which belongs to the field of semiconductor materials. The present invention is characterized in that the present invention adopts Pb(NO3) whose purity is 99.5%, SrCO3 whose purity is 99.5%, and TiO2 whose purity is 99.9% as raw materials. By regulating solid solubility, the present invention uses the negative thermal expansion property of PbTiO3 to prepare Pb<x>Sr<1-x>TiO3 ceramic materials whose thermal expansion coefficient is from-1.62*10<-5> to 3.42*10<-5>/DEG C, and a practical PTCR property is kept. The method is simple and is easy to operate and industrialize, and has important application value for developing series Pb<x>Sr<1-x>TiO3 ferroelectric ceramic materials.

Description

The preparation method of constant thermal expansion lead strontium titanate positive resistance temperature coefficient pottery

Technical field:

The invention belongs to field of semiconductor materials, particularly a kind of preparation method of ferroelectric ceramic material.

Background technology:

Lead strontium titanate (Sr, Pb) TiO ₃Be the novel ferroelectric semiconductive ceramic that developed recently gets up, it is as thermistor material, and its research starts from 1988, has and BaTiO ₃The similar typical positive resistance temperature coefficient of ceramic phase (PTCR) characteristic, this class pottery all has good ferroelectricity, is widely used.Zhao etc. have synthesized Pb with chemical coprecipitation _0.5Sr _0.5TiO ₃, study its PTCR characteristic ^[1]Usefulness ceramic high temperature sintering processs such as Somiya have been synthesized Pb _xSr _1-xTiO ₃(x=0.2,0.25,0.3), research solid solubility is to the influence of ferroelectric property, and all is 10.0 * 10 with the lines of expression coefficient of expansion that dilatometer has been measured three solutionizing compounds ^-6/ ℃ ^[2]

Reference

[1]J.Zhao，L.Li?and?Z.Gui，J.Eur.Ceram.Soc.，22(2002)1171-1175

[2]Y.Somiya，A.S.Bhalla?and?L.E.Cross，Int.J.Inorganic?Materials，3(2001)709-714.

Summary of the invention:

The objective of the invention is to utilize PbTiO ₃The negative expansion attribute, by the synthetic constant thermal expansion Pb of the mode that adds assorted solid solution _xSr _1-xTiO ₃The solutionizing compound, the Pb that the preparation thermal expansivity is complementary with certain positive resistance temperature characteristic (PTCR) _xSr _1-xTiO ₃Pottery.

A kind of preparation method of constant thermal expansion lead strontium titanate positive resistance temperature coefficient pottery is characterized in that preparing lead strontium titanate--Pb _xSr _1-xTiO ₃Raw material be: Pb (NO ₃) purity 99.5%, SrCO ₃Purity 99.5%, TiO ₂Purity 99.9%.Step of preparation process carries out in two steps, the first step: carry out thermal pretreatment before raw material mixes, after removing moisture, use the dehydrated alcohol wet mixing, grind with agate it is fully ground, after making it mix drying, under 30-50 MPa pressure well-mixed powder is pressed into disk, holds with crucible, overcoat is placed with the alumina crucible of a little PbO, 500 ℃ of reaction 8-12h under air atmosphere, 1100 ℃ are reacted 20-28h down; Second step: will grind again through the first step reaction product, and behind the compressing tablet,, cool to room temperature with the furnace, and be ground into powder, and just obtain flaxen single-phase Pb at 1100-1200 ℃ of following sintering 20-28h _1-xSr _xTiO ₃Compound.In order to prevent the volatilization of Pb, the initial reaction stage temperature is unsuitable too high, final sintering temperature according to the content of Pb what and decide.

For making the semiconductor of constant thermal expansion lead strontium titanate positive resistance temperature coefficient pottery, can be at synthetic solid solution compound Pb _1-xSr _xTiO ₃The middle 0.2-0.5mol%La that adds ₂O ₃, after mixing, grinding, sintering is 12 hours under 1200 ℃ of high temperature.

The invention advantage:

The invention has the advantages that and utilize PbTiO ₃The negative expansion attribute, by adjusting the mode of solid solubility, the preparation thermal expansivity is from-1.62 * 10 ^-5/ ℃ to 3.42 * 10 ^-5/ ℃ Pb _xSr _1-xTiO ₃Stupalith, and keep practical PTCR characteristic.This method is simple, easy handling and industrialization.

Embodiment:

Lead strontium titanate--Pb _xSr _1-xTiO ₃Raw material be: Pb (NO ₃) purity 99.5%, SrCO ₃Purity 99.5%, TiO ₂Purity 99.9%.Processing step carries out in two steps.The first step: carry out thermal pretreatment before the sample mix, its moisture that absorbs in air is fully broken away from.By given proportioning raw materials weighing, use the dehydrated alcohol wet mixing, grind with agate it is fully ground, it is mixed.After the drying, under 40MPa pressure well-mixed powder being pressed into diameter is 7mm, and thickness is the disk of 2mm.Hold with platinum crucible, overcoat is placed with the alumina crucible of a little PbO, 500 ℃ of reaction 10h under air atmosphere, and 1100 ℃ are reacted 24h down.Second step: will grind again through the first step reaction product, and behind the compressing tablet,, cool to room temperature with the furnace at 1100-1200 ℃ of following sintering 24h.In order to prevent the volatilization of Pb, the initial reaction stage temperature is unsuitable too high, final sintering temperature according to the content of Pb what and decide.Be ground into powder, just obtain flaxen single-phase Pb _1-xSr _xTiO ₃Compound.Table 1 is Pb _xSr _1-xTiO ₃The average intrinsic body thermal expansivity of (x=0,0.1,0.5,0.8,0.85,1) pottery, Curie temperature table.

Thermal expansivity (* 10 ^-5/ ℃)

Compound

Curie temperature

Four directions phase warm area/℃ cube phase warm area/℃/℃

PbTiO ₃ -1.62 RT~490 3.55 490~950 490

Pb _0.85Sr _0.15TiO ₃ -1.11 RT~400 3.81 400~900 400

Pb _0.80Sr _0.20TiO ₃ -0.52 RT~350 4.27 350~900 350

Pb _0.50Sr _0.50TiO ₃3.70 RT ~ below 900 RT

Pb _0.10Sr _0.90TiO ₃3.42 RT ~ below 900 RT

SrTiO ₃ 3.42 RT~900 -165

Annotate: RT is a room temperature.

Claims

1, a kind of preparation method of constant thermal expansion lead strontium titanate positive resistance temperature coefficient pottery is characterized in that preparing lead strontium titanate--Pb _xSr _1-xTiO ₃The raw material that adopts is: Pb (NO ₃) purity 99.5%, SrCO ₃Purity 99.5%, TiO ₂Purity 99.9%; Step of preparation process carries out in two steps, the first step: carry out thermal pretreatment before raw material mixes, after removing moisture, use the dehydrated alcohol wet mixing, grind with agate it is fully ground, after making it mix drying, under 30-50 MPa pressure well-mixed powder is pressed into disk, holds with crucible, overcoat is placed with the alumina crucible of a little PbO, 500 ℃ of reaction 8-12h under air atmosphere, 1100 ℃ are reacted 20-28h down; Second step: will grind again through the first step reaction product, and behind the compressing tablet,, cool to room temperature with the furnace, and be ground into powder at 1100-1200 ℃ of following sintering 20-28h.

2, the preparation method of lead strontium titanate positive resistance temperature coefficient pottery as claimed in claim 1 is characterized in that synthetic solid solution compound Pb _1-xSr _xTiO ₃In added 0.2-0.5mol%La ₂O ₃, after mixing, grinding, sintering is 12 hours under 1200 ℃ of high temperature.