Particle morphology, electrical conductivity, crystal and electronic structures of hydrothermally synthesized (Ce,Sr)PO₄

We focused on Sr-substituted CePO₄—i. e., (Ce,Sr)PO₄—with the monazite structure and synthesized the orthophosphates hydrothermally. As for the obtained products, we investigated the particle morphologies by SEM and electrical conduction properties by conductivity measurements. In order to estimate the crystal and electronic structures, neutron and synchrotron X-ray diffraction measurements were also carried out. As a result, it was found that (Ce,Sr)PO₄ with a single phase of the monazite structure was successfully prepared by the hydrothermal method and the substitution amount of Sr was almost equal to the nominal one. It was also demonstrated that a powder morphology of the (Ce,Sr)PO₄ depended on the synthetic conditions; i.e, concentrations of cation sources and pH of aqueous solution in the hydrothermal process. The Sr-substituted sample showed much higher conductivities than the unsubstituted one, in the same way as the (Ce,Sr)PO₄ synthesized by other methods reported previously.