The Preparation And Properties Of BST Pyroelectric Ceramics

(Ba1-xSrx)TiO3 (BST) ceramics have higher pyroelectric efficient, higher dielectric constant, lower dielectric loss and higher detecting merits than other common pyroelectric materials, BST ceramics have the advantages of ambient temperature operation, low power consumption, low in-service costs, low weight and compactness. So BST ceramics have been widely used in uncooled infrared focal plane arrays (UFPA) and have involved more interesting.The influences of Mn-doping and Ca-doping to the properties of samples have been studied and the influence of sintering temperature on ceramics properties was discussed too. The results indicate that proper Mn doping, has little influences on the samples'dielectric constant, but it can reduce the samples'dielectric loss obviously; the ferroelectric properties become bad, but the pyroelectric properties become better. The sample doped with 0.5 at% was prepared, whose dielectric loss,dielectric constant and pyroelectric coefficient were 0.4%, 3200 and 20×10-8C㎝-2K-1 at room-temperature, respectively. And proper Ca doping can reduce the samples'dielectric constant and improve pyroelectric coefficient, but the dielectric loss is increased too. With the sintering temperature rising, the dielectric loss will become bigger, the dielectric coefficient and the pyroelectric coefficient will have little change. When the quantity of Ca doping is 3 at% and the sintering technique is for 1 hour at 1300℃, The sample will be prepared, whose pyroelectric coefficient and figure of merit are 19×10-8C㎝-2K-1, 2.9×10-5Pa-1/2 at room-temperature, respectively.The theory about dielectric bolometer mode of BST was introduced, and the equation about pyroelectric coefficient of BST under dielectric bolometer (DB) mode was deduced, according to which computer-aided system for measuring BST ceramics'pyroelectric coefficient was manufacture. The dielectric properties of the samples can be measured by the measuring system under 0-500V DC bias-field and 5-120℃. The date can be collected through RS232 serialport, and the curve of dielectric coefficient as temperature instantly can be educed automatically. Through processes of averaging, fitting and deriving, the curve of dielectric loss as temperature, the curve pyroelectric coefficient as temperature and the curve of figure of merit as temperature can be educed.