An Aurivillius phase, Bi2SrTa2O9, which consists of perovskite-like slabs and bismuth oxide sheets, was treated with 3 M hydrochloric acid for 72 h, and the resultant product was characterized. Scanning electron microscopy investigation indicated that no morphological change occurred during the acid treatment. X-ray diffraction (XRD) analysis revealed that the product exhibited tetragonal symmetry with a = 0.39l ± 0.004 nm and c = 0.98 ± 0.01 nm, and the a parameter is consistent with a typical value for cubic perovskite oxides. High-resolution electron microscopy (HREM) observations along both  and  showed that the structure of the perovskite-like slabs in Bi2SrTa2O9 was retained after the acid treatment. The compositional analyses revealed the loss of a large portion of bismuth and a part of strontium (present in the bismuth oxide sheets due to B ↔ Sr disorder) and the introduction of protons. These observations indicate that the bismuth oxide sheets in Bi2SrTa2O9 were selectively leached and that protons were introduced into the interlayer space to form a protonated layered perovskite, H1.8[Sr0.8Bi0.2Ta2O7]. Though diffraction techniques (XRD and electron diffraction) demonstrated that an average structure of H1.8[Sr0.8Bi0.2Ta2O7] consisted of perovskite-like slabs stacked without displacement, HREM observation along  demonstrated that both a simple stacking sequence without displacement (P-type) and a stacking sequence with a relative displacement by (a + b)/2 (I-type) were present in H1.8[Sr0.8Bi0.2Ta2O7].
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry