Synthesis and Properties of Sr ₉ Ce ₂ W ₄ O ₂₄ Quaternary Perovskite

We report details on the synthesis and properties of strontium cerium tungstate, Sr₉Ce₂W₄O₂₄, a quaternary perovskite that has not yet been synthesized in pure form. Room-temperature powder X-ray diffraction (XRD) identified the most probable space group as tetragonal I4₁/a. X-ray photoelectron spectroscopy confirmed that the material obtained after synthesis contained cerium in both 3+ and 4+ charge states, as well as tungsten in 5+ and 6+ states. Temperature-dependent Raman and XRD measurements done at 1 atm air and N₂ excluded the possibility of a phase transition occurring within the 8-873 K; however, when exposed to air, the compound decomposes to a mixture of various salts and oxides just above 573 K. When compressed at room temperature, a possible transition toward lower-symmetry, monoclinic (C2/c or C2/m) space groups was detected between 12.5 and 15 GPa.