Formation of SrBi2Ta2O9 .2. Evidence of a bismuth-deficient pyrochlore phase

A bismuth-deficient pyrochlore phase has been observed in both powder and film samples fired at 775 degrees C. The estimated stoichiometry of this pyrochlore (based on calculated diffraction patterns) was Sr-0.2(Sr0.5Bi0.7)Ta2O6.75. This bismuth-deficient pyrochlore phase may be considered deleterious to the formation of the SrBi2Ta2O9 ''SET'' ferroelectric compound since a significant presence of this pyrochlore compound implies a large deviation from the desired cation ratios. Additionally, films prepared on platinized silicon substrates indicate the SBT phase formation may be encouraged by the substrate; there appears to be some 00l preferential orientation for stoichiometric SBT thin films.