Stability and formation of pyrochlore phase in doped Sr0.8Bi2.3Ta2O9 thin films

Ferroelectric thin films of bismuth-containing layered perovskite Sr0.8Bi2.3Ta2−xMxO9 (SBTM), where M is V, Ti, W, and Zr, have been prepared on Pt/Ti/SiO2/Si substrates using the metal-organic decomposition method. The effect of the incorporated B-site cations on pyrochlore phase formation and microstructure evolution of SBTM films was investigated. The pyrochlore phase formation has been identified due to out-diffusion of titanium from underneath platinum layer to participate in the reaction with the films. Furthermore, the formation of pyrochlore phase in the SBTM films has been observed strongly dependent on the characteristics of incorporated M cation. The substitution of both W and V for Ta leads to the formation of pyrochlore phase at lower annealing temperature (750–800 °C). On the other hand, the addition of Zr can retard the formation of pyrochlore phase from 850 to 900 °C. A model based on the binding energy of octahedral structure is used to elucidate the formation and stability of the pyrochlore phase present in the SBT film.