title: High-pressure synthesis, crystal structure, and unusual valence state of novel perovskite oxide CaCu3Rh4O12.
abstract: A novel perovskite oxide, CaCu3Rh4O12, has been synthesized under high-pressure and high-temperature conditions (15 GPa and 1273 K). Rietveld refinement of synchrotron X-ray powder diffraction data indicates that this compound crystallizes in a cubic AA'3B4O12-type perovskite structure. Synchrotron X-ray absorption and photoemission spectroscopy measurements reveal that the Cu and Rh valences are nearly trivalent. The spectroscopic analysis based on calculations suggests that the appropriate ionic model of this compound is Ca(2+)Cu(∼2.8+)3Rh(∼3.4+)4O12, as opposed to the conventional Ca(2+)Cu(2+)3Rh(4+)4O12. The uncommon valence state of this compound is attributed to the relative energy levels of the Cu 3d and Rh 4d orbitals, in which the large crystal-field splitting energy of the Rh 4d orbitals is substantial.
authors.affiliation: Nanoscience and Nanotechnology Research Center, Osaka Prefecture University , 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570, Japan.
authors.forename: Ikuya
authors.initials: I
authors.lastname: Yamada
authors.forename: Mikiko
authors.initials: M
authors.lastname: Ochi
authors.forename: Masaichiro
authors.initials: M
authors.lastname: Mizumaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hariki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uozumi
authors.forename: Ryoji
authors.initials: R
authors.lastname: Takahashi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Irifune
mesh_terms: D017610:Calcium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006358:Hot Temperature; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D033362:Powder Diffraction; D011312:Pressure; D014025:Titanium / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: D017610:Calcium Compounds; D010087:Oxides; C059910:perovskite; D014025:Titanium