Abstract
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 and decomposes by oxygen loss at higher temperatures. In-situ x-ray diffraction measurements showed, for the precursor batch examined, the formation of CeP2O7 in two distinct stages. At room temperature CeP2O7 is pseudocubic, but probably triclinic, displaying positive thermal expansion below ~ 115 �C. Above this temperature there is a transition to cubic symmetry (Pa-3) with the linear coefficient of thermal expansion going to zero at ~ 450 �C and becoming negative at higher temperatures. CeP2O7 probably undergoes two phase transitions on compression below ~ 10.5 GPa. The phase existing between 0.65 and ~ 5 GPa is soft with an average bulk modulus of ~18 GPa.
