PHASE-TRANSITION IN FERROELECTRIC SRBI2TA2O9 THIN-FILMS WITH CHANGE OF HEAT-TREATMENT TEMPERATURE

Changes in the composition and the crystal structure of micro-grains h ave been studied using transmission electron microscopy (TEM) and ener gy dispersive X-ray microanalysis in order to clarify the phase format ion of ferroelectric SrBi2Ta2O9 (SBT) with heat-treatment at 650-750 d egrees C. Micrograins crystallized at 650 degrees C begin to change to bismuth-layer-structure-family (BLSF) grains at temperatures exceedin g 700 degrees C, and form pure-BLSF phase grains at 800 degrees C, Hen ce, a micrograins phase exists in thin films at 650-750 degrees C and we determined that the bismuth composition in these grains decreases. Using selected diffraction and high-resolution TEM, we found that a py rochlore phase was formed in the bismuth-poor micrograins that were he at treated at 750 degrees C, The formation of pyrochlore made pure-pha se BLSF difficult to obtain.