Publikationsdatum:
2016-02-20
Beschreibung:
Despite wide studies of Na 0.5 Bi 0.5 TiO 3 , structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na 0.5 Bi 0.5 TiO 3 -CaTiO 3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na 0.5 Bi 0.5 TiO 3 as the end member of this material group. X-ray diffraction patterns for Na 0.5 Bi 0.5 TiO 3 -CaTiO 3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na 0.5 Bi 0.5 TiO 3 ), whereas structure of pure Na 0.5 Bi 0.5 TiO 3 can be considered, assuming coexistence of rhombohedral and orthorhombic phases. This allows one to avoid appearance of a large difference of rhombohedral distortions between the unpoled and poled Na 0.5 Bi 0.5 TiO 3 , if the rhombohedral distortion is calculated as for single R3c phase. Features of dielectric permittivity, corresponding to the observed structural phase transition, are identified. It is discussed that the rhombohedral R3c phase is responsible for appearance of the frequency-dependent shoulder of dielectric permittivity temperature dependence, characteristic for unpoled Na 0.5 Bi 0.5 TiO 3 .
Print ISSN:
0021-8979
Digitale ISSN:
1089-7550
Thema:
Physik
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