High-pressure Synthesis of PbCrO3

A new compound with the composition PbCrO₃, with Cr in the valence state of 4, was synthesized at high pressures above a pressure-temperature line extending from about 50 kbars at 750°C to 60 kbars at 1450°C. PbCrO₃ can be quenched and retained at 1 atm but decomposes on heating above 275° C at the same pressure. PbCrO₃ is considered to be an equilibrium phase at high pressures because it was synthesized from mixtures of PbO: CrO₂ as well as from several other mixtures of compounds in the Pb-Cr-0 system. The new phase has the cubic perovskite structure and is the only known compound with Cr⁴⁺ in an octahedral site. PbCrO₃ crystallizes primarily as black cubes which are often twinned on (111).