X-ray photoelectron study of calcium cerium titanate ceramics

Abstract

The elemental and ionic quantitative compositions and oxidation states of elements in the ceramics CaCe0.9Ti2O6.8 (I) and CaCeTi2O7 (II)-matrices for long-term storage of long-lived radionuclides constituting hi-h-level radioactive wastes-are studied by X-ray photoelectron spectroscopy. Compound I, obtained at a pressure of 300 MPa and T = 1400degreesC in air, has two types of surface cerium ions, 63 at. % Ce3+ and 37 at. % Ce4+; compound II, fabricated at a pressure of 300 MPa and T= 1300degreesC in an oxygen atmosphere, also has two types of surface ions, 36 at. % Ce3+ and 64 at. % Ce4+, which agrees satisfactorily with X-ray powder diffraction and scanning, electron microscopy data. On exposure to environmental conditions, calcium and/or cerium carbonates can form on the surface of the ceramics under consideration, which entails their failure.