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We show that substrate-free crystallized barium titanate (BaTiO[SUB3]) films adopt a hexagonal structure, whereas substrate-supported films assume the commonly observed tetragonal phase. However, in contrast to the known hexagonal BaTiO[SUB3], the substrate-free crystallized films demonstrate a small but measurable pyroelectric effect, and do not exhibit phase transitions in the 25-423 K temperature range. Thus the substrate-free crystallized BaTiO[SUB3] represents a heretofore unreported crystallographic modification of BaTiO[SUB3]. [ABSTRACT FROM AUTHOR]

Quasi-amorphous BaTiO3 thin films demonstrate pyroelectricity and piezoelectricity of a magnitude of 5–15% of bulk BaTiO3, despite the fact that X-ray and electron diffraction data do not reveal detectable crystallites in this material. Therefore, the pyroelectric and piezoelectric effects must be attributed to a local dipole ordering, which is induced by the high compressive stress in the films. The non-crystalline films were prepared by passing amorphous BaTiO3 layers deposited on a Si(1 0 0) substrate through a temperature gradient. [Copyright &y& Elsevier]