Thermal expansion of (Ca1−xPux)TiO3

The phase relationship between PuO2−x and CaTiO3 at room temperature was investigated by X-ray diffraction. It was found that Pu was soluble to at least 20 mol% in CaTiO3 in Ar–8% H2. Solubility of Pu in CaTiO3 was extremely limited (below 5 mol%) under oxidizing condition. The thermal expansion of (Ca1−xPux)TiO3 (x=0–0.15) was investigated in the temperature range from room temperature to 1273 K by high-temperature X-ray diffraction. The linear thermal expansion coefficients showed considerable anisotropy for the orthorhombic Pbnm structure and decreased with increasing Pu content. The structural phase-transition temperatures were estimated from the lattice constants and were relatively insensitive to the content of Pu dopant. The estimated melting point increased with increasing Pu content, indicating that the thermodynamic stability of CaTiO3 increased with the addition of Pu.