Hydroxide precursors to produce nanometric YCrO₃: Characterization and conductivity analysis

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• 作者：A. Durá ; n^a ; ^{dural@cnyn.unam.mx} ; C. Meza F^a ; Gregorio Guadalupe Carbajal Arizaga^b ; ^{gregoriocarbajal@yahoo.com.mx}
• 关键词：A. Ceramics ; B. Chemical synthesis ; D. Ferroelectricity
• 刊名：Materials Research Bulletin
• 出版年：2012
• 期刊代码：60_00255408
• 类别：ms
• 出版时间：June, 2012
• 卷：47
• 期：6
• 页码：1442-1447
• 文件大小：789 K

摘要

A precursor to produce perovskite-type YCrO₃ was precipitated by bubbling gaseous ammonia into an yttrium/chromium salts solution. X-ray diffraction showed that the as-prepared powders were amorphous. Thermal treatment between 1273 and 1373 K, leads to formation of polycrystalline YCrO₃ with crystal sizes around 20 nm. High resolution X-ray photoelectron spectra showed uniform chemical environment for yttrium and chromium in the amorphous hydroxide and crystalline YCrO₃. Shifts between Y 3d_5/2 and Cr 2p_3/2 binding energy suggest redistribution or charge transfer between yttrium and chromium ions in the YCrO₃ structure. The electrical properties of YCrO₃, whose precursors were precipitated with gaseous ammonia are different than those prepared by combustion synthesis. Electrical conductivity presents a sudden increase at 鈭?73 K, which is associated to the grain size and morphology of the crystallites. The redistribution of charge between Y(III) and Cr(III) is thermally activated by the hopping of small-polarons, which are characterized by the Arrhenius law as the conductive mechanism.