ON THE DIFFUSION OF CE INTO EU2CUO4-Y COMPOUNDS

The diffusion of Ce in polycrystalline samples of Eu2-xCexCuO4-y (0.0 less than or equal to x less than or equal to 0.18) prepared from a so l-gel precursor and sintered at several temperatures 150 degrees C les s than or equal to T less than or equal to 950 degrees C was investiga ted. The results of X-ray powder diffraction revealed that complete di ffusion of Ce into the Eu2CuO4-y matrix occurs in samples sintered at T = 950 degrees C, which is below the eutectic temperature. It was als o observed that the Ce diffusion monotonically increases with increasi ng x, suggesting that the Eu2-xCexCuO4-y (0.0 less than or equal to x less than or equal to 0.18) system forms a true chemical solid solutio n. The solubility limit of Ce in this series was found to be close to x = 0.15. An accurate analysis of the full width at half maximum of th e X-ray diffraction peaks reveals an inhomogeneous Ce distribution in samples sintered for short time intervals. An improvement of the homog eneity of Ce was found in samples sintered for longer times. Results o f differential thermal analysis and thermogravimetry were found to be in complete agreement with the X-ray diffraction data. We also found t hat the peritectic temperature T-p increases with increasing Ce conten t in this series.