Preparation of Layered Ferroelectric Bi 2 SrTa 2 O 9 Single-Crystal Platelets

• Published in: Japanese Journal of Applied Physics Vol. 35; no. 5A; p. L564
• Main Authors: Suzuki, Masayuki, Nagasawa, Naomi, Akio Machida, Akio Machida, Takaaki Ami, Takaaki Ami
• Format: Journal Article
• Language: English
• Published: 01-05-1996
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.35.L564

Layered ferroelectric Bi
2
SrTa
2
O
9
is attracting much attention as a fatigue-free material for ferroelectric nonvolatile memory devices. We have successfully synthesized this single-crystal platelet without any impurity phases by the self-flux method. The largest crystals measure about 1 mm×1 mm×5 µ m, and the lattice parameters were estimated to be
a
=0.5528 nm and
c
=2.498 nm, assuming a tetragonal cell. The chemical composition is 1.92:1.10:2.00 in an atomic ratio of Bi:Sr:Ta, from ICP-AES analysis. By wet etching, the crystal structure was found to be decomposed anisotropically, leaving only the
c
-axis framework. The step height of the topmost surface observed by atomic force microscopy (AFM) was 1.2 to 1.3 nm, which corresponds to half of the
c
-axis length (about 2.5 nm). Through thermal analysis, the thermal anomaly originating in ferroelectric-paraelectric phase transition was not observed and there was little evaporation of Bi compounds.