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Thermal and structural studies showed that SrBi 2 Ta 2 O 9 undergoes ferroelectric-intermediate and intermediate-paraelectric phase transitions at 608 K ( T c ) and 850 K ( T *), respectively, while Bi-rich Sr 0.85 Bi 2.1 Ta 2 O 9 at 510 K ( T o ) and 670 K ( T c ). On heating, SrBi 2 Ta 2 O 9 still remains to be orthorhombic above T c , and then changes to tetragonal above T *. The TaO 6 is a distorted octaheron along the c -axis even in the paraelectric phase, and locates in antiparallel manner above T *. Below T c , this crystal favors canted arrangements of TaO 6 , resulting in the net polarization along the a -axis. It was clarified that SrBi 2 Ta 2 O 9 shows a canted weak ferroelectricity, analogous to weak ferromagnetism with Dzialoshinski-Moriya interaction. [ABSTRACT FROM AUTHOR]

Accurate electron densities of single crystals of paraelectric ZnO and ferroelectric Li-doped ZnO at 19 K were analyzed by the maximum entropy method. The change in electron density distribution around Zn and O atoms indicates that the 3 d -electron at the Zn site transfers to the Zn-O bond by Li substitution. [ABSTRACT FROM AUTHOR]

Crystal structure of Bi-layered perovskite SrBi 2 Ta 2 O 9 was studied at 1000 K by X-ray diffraction. Rietveld analysis confirmed antiparallel arrangements of TaO 6 octahedra in the high-temperature paraelectric phase (tetragonal 14/mmm, R wp =7.37%). The TaO 6 octahedra are distorted along the c -axis. This crystal favors canted octahedral arrangements below T c (608 K). These result in net spontaneous polarization along the a -axis. We report the first observation of canted ferroelectricity or weak ferroelectricity in SrBi 2 Ta 2 O 9 . [ABSTRACT FROM AUTHOR]