Quasi-amorphous pyro- and piezo- electric SrTiO3.

Recent publications about quasi-amorphous BaTiO3 materials have demonstrated that non-crystalline ionic solids can exhibit pyro- and piezo- electricity. This posed a question whether the quasi-amorphous state is unique to BaTiO3 or other compounds can form non-crystalline polar phases. We report that pulling through a temperature gradient converts amorphous thin ($<$100 nm) films of SrTiO3 into a pyro- and piezoelectric phase, which is nevertheless non-crystalline according to XRD and SEM. Thus SrTiO3 may form a quasi-amorphous phase. This implies that: (1) the quasi-amorphous state is not unique to BaTiO3 but other compounds may form similar phases; (2) polarity of a compound in a quasi-amorphous phase is not related directly to the polarity of this compound in a crystalline form. In this view, one may expect that other quasi-amorphous phases will be found. Owing to the simplicity of their preparation, quasi-amorphous materials are very promising for future pyroelectric and piezoelectric devices that can be integrated with modern semiconductor technology.