Degradation of ferroelectric SrBi2Ta2O9 materials under reducing conditions and their reaction with Pt electrodes

The degradation of ferroelectric SrBi2Ta2O9 in an H-2-containing reducing atmosphere and its recovery by subsequent annealing in oxygen have been reproduced experimentally by using bulk ceramic samples. SrBi2Ta2O9 decomposes into Bi metal and Sr-Ta oxide(s) in H-2 above 300 degrees C, and the decomposition rate increases as the annealing temperature rises. The recovery of SrBi2Ta2O9 is achieved through oxidation of Bi metal into beta-Bi2O3, followed by a reaction of beta-Bi2O3 and Sr-Ta oxide(s). In the presence of Pt, which is usually used as an electrode, the decomposition of SrBi2Ta2O9 is accelerated. Bi-Pt alloy and Bi-Pt oxide are produced under the reducing and oxidizing conditions, respectively. Our findings have important implications concerning the degradation of SrBi2Ta2O9 capacitors and the reaction between SrBi2Ta2O9 materials and Pt electrodes during thin-film device fabrication. (C) 1999 American Institute of Physics. [S0003-6951(99)04044-9].