General rules for predicting phase transitions in perovskites due to octahedral tilting.
Recent experiments on several oxide perovskites reveal that they undergo tilt phase transitions to higher-symmetry phases on increasing pressure and that dTc/dP<0, contrary to a general rule previously proposed for such zone-boundary transitions. We show that the negative slope of the phase boundary is a consequence of the octahedra in these perovskites being more compressible than the extra-framework cation sites. Conversely, when the octahedra are stiffer than the extra-framework cation sites, the phase transition temperatures increase with increasing pressure, dTc/dP>0.
Angel
R J
RJ
Virginia Tech Crystallography Laboratory, Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24060, USA. rangel@vt.edu
Zhao
J
J
Ross
N L
NL