Evidence for Pb-O covalency in tetragonal PbTiO3.
Accurate charge-density distributions of cubic and tetragonal PbTiO3 and BaTiO3 have been obtained by the MEM(maximum entropy method)/Rietveld analysis using synchrotron-radiation powder data. The Pb-O bonds in tetragonal PbTiO3 show rather strong covalency, while those in cubic PbTiO3 are ionic. This is the clear evidence of the Pb-O hybridization in tetragonal PbTiO3, which has been theoretically predicted as a key factor of much larger ferroelectricity of this substance than that of BaTiO3. Tetragonal PbTiO3 forms a layered structure of a two-dimensional covalent-bonding network consisting of the Ti-O5 pyramid.
Kuroiwa
Y
Y
Department of Physics, Okayama University, Okayama 700-8530, Japan. kuroiwa@science.okayama-u.ac.jp
Aoyagi
S
S
Sawada
A
A
Harada
J
J
Nishibori
E
E
Takata
M
M
Sakata
M
M