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The x-ray fluorescence holography technique is applied to perovskite (Ba0.9Ca0.1)TiO3 ferroelectrics in order to investigate the local structures around the Ca and Ba ions at the A-site. While the A-site atomic images around the Ba ion can be well understood based on the BaTiO3 structure, those around the Ca ion are located at the closer positions to the emitter. Furthermore, the shape of the atomic image around the Ca ion is elongated in the radial direction. These features clearly show the local lattice contraction around the Ca ion and a significant displacement of the Ca ions from the ideal position. On the basis of the detailed analysis of the position and the shape of the atomic image around the Ca ion, it is found that the Ca ions are displaced by ∼0.36 Å in the ⟨111⟩ direction, and the surrounding Ba ions are displaced by ∼0.22 Å in the ⟨100⟩ direction. The present results indicate that the doped Ca ions activate the A-site polarization of this compound, which can lead to an enhancement of the ferroelectric and piezoelectric performances.

ABSTRACT:Isotherms for absorption of iodine by various polymers have been measured at 25°C in aqueous media. Poly(3-vinyl-10-methylphenothiazine) (PVMP), poly(4-vinylpyridine), and poly(tetramethylene ether glycol) absorb 3.0 g, 2.3 g, and 1.8 g of iodine, respectively, per 1.0 g of the polymer when dipped in a 0.05 M aqueous solution of 12 containing KI at 25°C. 6-Nylon, poly(vinyl alcohol), poly(acrylonitrile), poly(acrylamide) absorb 1.7 g, 1.5 g, 1.2 g, and 0.82 g of iodine, respectively, per 1.0 g of the polymer when dipped in a 0.10 M aqueous solution of 12 under the same conditions. Except for 6-nylon, the dependence of the amount of absorbed iodine on [12] K obeys a Langmuir-type equation obtained assuming the equilibrium, 12 +polymer=='" 12.-polymer complex. The equilibrium constant K ranges from 13 M-1 (for poly(vinyl alcohol)) through 53 M-1 (for PVMP). Cyclic voltammograms obtained using a polymer electrode coated on a Pt wire show the occurrence of smooth oxidation and reduction of 1-and 12 , respectively, on the surface of the polymer electrode and inside of the polymer electrode.