Anomalous high temperature crystal structure behaviour of PrCo0.5Cr0.5O3

摘要

Mixed praseodymium cobaltite-chromite PrCo_0.5Cr_0.5O₃ with dimensionally (pseudo)-cubic orthorhombic perovskite structure was obtained by solid state reaction in air at 1573 K. Crystal structure parameters were derived from high-resolution X-ray synchrotron powder diffraction data collected in situ in a broad temperature range of 298-1173 K. Analysis of the results obtained revealed anomalous thermal expansion of PrCo_0.5Cr_0.5O₃, which is reflected in a sigmoidal temperature dependence of the unit cell dimensions and in abnormal increase of the thermal expansion coefficients with a broad maxima near 870 K. The observed anomalies are associated with the changes of spin state of Co3+ ions and temperature induced insulator-metal transition occurred in PrCo_0.5Cr_0.5O₃.