（A-Site and B-Site Charge Orderings in an s-d Level Controlled Perovskite Oxide PbCoO3 ）
Y. Sakai, J. Y. Yang, R. Yu, H. Hojo, I. Yamada, P. Miao, S. Lee, S. Torii, T. Kamiyama, M. Lezaic, G. Bihlmayer, M. Mizumaki, J. Komiyama, T. Mizokawa, H. Yamamoto, T. Nishikubo, Y. Hattori, K. Oka, Y. Y. Yin, J. H. Dai, W. M. Li, S. Ueda, A. Aimi, D. Mori, Y. Inaguma, Z. W. Hu, T. Uozumi, C. Q. Jin, Y. W. Long and M. Azuma
J. Am. Chem. Soc. 139, 4574 (2017)
Perovskite PbCoO3 synthesized at 12 GPa was found to have an unusual charge distribution of Pb2+Pb4+ 3Co2+ 2Co3+ 2O12 with charge orderings in both the A and B sites of perovskite ABO3. Comprehensive studies using density functional theory (DFT) calculation, electron diffraction (ED), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), hard X-ray photoemission spectroscopy (HAXPES), soft X-ray absorption spectroscopy (XAS), and measurements of specific heat as well as magnetic and electrical properties provide evidence of lead ion and cobalt ion charge ordering leading to Pb2+Pb4+ 3Co2+ 2Co3+ 2O12 quadruple perovskite structure. It is shown that the average valence distribution of Pb3.5+Co2.5+O3 between Pb3+Cr3+O3 and Pb4+Ni2+O3 can be stabilized by tuning the energy levels of Pb 6s and transition metal 3d orbitals.