Synthesis, Symmetry and Physical Properties of Cerium Pyrophosphate

摘要: CeP2O7, a close structural relative of ZrP2O7, and many other MIVX2O7 (X – P, V, As) phases, forms on heating Ce(HPO4)2·xH2O between ∼300 600 °C decomposes by oxygen loss at higher temperatures. In-situ X-ray diffraction measurements showed, for some precursor batches, the formation CeP2O7 in two distinct stages. At room temperature, is pseudocubic, but probably triclinic, displaying positive thermal expansion below ∼115 °C. Above this there transition to cubic symmetry (Pa3) with linear coefficient going zero ∼450 becoming negative undergoes phase transitions compression ∼10.5 GPa. The existing 0.65 ∼5 GPa soft an average bulk modulus ∼18