ABSTRACT
A series of P5+ - doped La2Mo2O9 phases with different concentrations of P5+ were prepared using conventional solid-state reactions. The formation of phase-pure P5+-doped La2Mo2O9 has been monitored by powder X-ray diffraction, thermal analysis, conductivity measurements, Raman, and FT-IR absorption techniques. The structure and lattice parameters of La2Mo2-yPyO9-y/2 are obtained from Rietveld refinement. The effect of substituting P for Mo reveals that the phase transition which occurs in La2Mo2O9 around 560 °C disappears when y > 0.02, as demonstrated by thermal analysis. Pure P5+-doped phases with monoclinic structure (α-form, the space group P21) were observed for the concentration of optically active ions up to y = 0.02. When the concentration of P5+ ions is higher, a cubic structure (ß-form, the space group P213) starts to appear. However, up to the concentration of y = 0.03 of the P5+ ion a mixture of the monoclinic and cubic phases has been observed. From infrared and Raman analysis it is confirmed that different vibration modes arise from the vibration of molybdenum-oxygen bands. Mo-O bond lengths are also found to be independent of P-doping.
