Temperature‐Induced Intersite Charge Transfer Involving Cr ions in A‐Site‐Ordered Perovskites ACu3Cr4O12 (A=La and Y) |
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| Authors: | Dr Shoubao Zhang Prof Takashi Saito Dr Masaichiro Mizumaki Prof Yuichi Shimakawa |
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| Affiliation: | 1. Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611‐0011 (Japan), Fax: (+81)?774‐38‐3118;2. Japan Synchrotron Radiation Research Institute, SPring‐8, 1‐1‐1 Kouto, Sayo‐cho, Sayo‐gun, Hyogo 679‐5198 (Japan);3. Japan Science and Technology Agency, CREST, Gokasho, Uji, Kyoto 611‐0011 (Japan) |
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| Abstract: | Changes in the valence state of transition‐metal ions in oxides drastically modify the chemical and physical properties of the compounds. Intersite charge transfer (ISCT), which involves simultaneous changes in the valence states of two valence‐variable transition‐metal cations at different crystallographic sites, further expands opportunities to show multifunctional properties. To explore new ISCT materials, we focus on A‐site‐ordered perovskite‐structure oxides with the chemical formula AA′3B4O12, which contain different transition‐metal cations at the square‐planar A′ and octahedral B sites. We have obtained new A‐site‐ordered perovskites LaCu3Cr4O12 and YCu3Cr4O12 by synthesis under high‐pressure and high‐temperature conditions and found that they showed temperature‐induced ISCT between A′‐site Cu and B‐site Cr ions. The compounds are the first examples of those, in which Cr ions are involved in temperature‐induced ISCT. In contrast to the previously reported ISCT compounds, LaCu3Cr4O12 and YCu3Cr4O12 showed positive‐thermal‐expansion‐like volume changes at the ISCT transition. |
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| Keywords: | charge transfer high‐pressure synthesis perovskite phases valence degeneracy |
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