Investigation of Bi-Layer Structure Ceramics

Abstract

P i e m e l e c t r i c ceramic with BL-layer s t ruc tu re are good transducer materials being suitable to use i n high temperature. They possess high Curie tenperature, low d i e l e c t r i c constant and the s tab1 In view of t h i s matter, it is a t t r a c t i v e to us to fur ther develop material and explore why they can provide these characteristics. behavior under the stress and/or the temperat Jl . x 2 1 t h e performances of these Experiments and r e s u l t s 1. Preparation Ceramic samples with t h e mlecular f o m l a Bi4LMI'i&2awere grepared and tested i n t h i s paper, where , Sr , Ba" and Pb" . Their abbreviat i o n are BCT, BST, BBT and BFT. For the ceramics with Bi-layer structure, owing to t h e i r very high coercive f i e l d Ec, they have to bear serious poling condition, so as t o rmst have high density and high hanzgeneity as f a r as possible. In our experiment t he s t i r r i n g dry method w a s used a f t e r t he batches had been wet mixed to ensure high density and high hcrsgeneity f o r these ceramics. The dens i t ies of these ceramic samples with d i f f e ren t ampositions and s in t e r ing temperatures are listed i n Tab. 1, and Fig. 1 shows t h e i r corresponding microstructure. Tab. 1 Sintering, dielectric and p iezoe lec t r ic pmperties of BCT, BST, BBT and BPT ceramics. Fig. 1. Electron micrograph of BCT, BST, BBT and BKT ceramics. x 5000 2. Dielectric and p iezoe lec t r ic proper t ies measured on d i f f e ren t samples with diameter of 10 mn and thickness of 0.5 m. These r e s u l t s are shown i n Tab. 1 and Fig. 2. I t shows tha t t he d i e l e c t r i c and p iezoe lec t r ic proper t ies of these ceramics are bas ica l ly similar t o each other: d 3 =16-20~16'~ c /n , E~l60-250, tand=0.005-0.02, except the d i f f e ren t Curie temperatures ranging f m 400°C to-48W°C. The saturated fe r roe lec t r i c hys te res i s 1pps of BST ceramics at roan tanperature and 150 C were also measured by using quasis tatic electric f i e l d method (0.1 c / s ) . The values of spontaneous polarization Ps, coercive f i e l d E c and saturated electric f i e l d E s determined from these loops shown i n Fig. 3 are of 1 2 , u c / ~ , 80 Kv/m and 150 Kv/m a t room temperature respectively. Dielectric and p iezoe lec t r ic proper t ies were 3. S t a b i l i t i e s of proper t ies The ceramics samples with the abbreviation BST were selected to measure t h e i r s t a b i l i t i e s . (1) S t a b i l i t y of p iezoe lec t r ic coef f ic ien t dS3 with temperature. The s t a b i l i t y of p iezoe lec t r ic coef f ic ien t 105 CH2358-O/R6/0000-0165 $1 d0 @ 19R6 IEEE Tab. 2 Change i n capacitance C and p iezoe lec t r ic e f f i c i e n t dm of BST ceramics a f t e r heat treatment