首页>
外文期刊>journal of applied physics
>A systematic experimental and theoretical investigation of the grainhyphen;boundary resistivities ofnhyphen;doped BaTiO3ceramics
【24h】
A systematic experimental and theoretical investigation of the grainhyphen;boundary resistivities ofnhyphen;doped BaTiO3ceramics
The electrical resistivities, currenthyphen;voltage characteristics, and thermopowers of a series ofnhyphen;doped BaTiO3ceramics having systematically varying resistivity anomalies (posistor or PTC effect) are analyzed in light of the theoretical description of the grainhyphen;boundary resistivity by a Schottkyhyphen;type potential barrier model (Heywangrsquo;s barrier). The observed currenthyphen;voltage dependences agree well with this model over a wide voltage range. However, the agreement between the theoretical and experimental temperature curves of the lowhyphen;voltage resistivities is weak if the surface acceptor states, which result as recently suggested from an excess of barium vacancies in the immediate vicinity of the grain surface, are assumed to be at the same energy. Satisfactory agreement is obtained when the acceptor states are distributed over a certain energy interval. An estimate of the surface charge then reveals that the resistivity below the Curie point is governed by a residual potential barrier originating from an excess of surface charge which cannot be compensated even by an optimum alignment of the spontaneous polarization.
展开▼
