Synthesis and characterization of (La1-xMx)(2)Mo2O9-delta ; M=Ca2+, Sr2+ or Ba2+

The system (La1-xCax)(2)Mo2O9-delta was characterized in the region x = 0.01 less than or equal to x less than or equal to 0.15 by slow-scan powder X-ray diffraction measurements in order to determine the solubility limit of CaO. For the sake of comparison, the same was repeated for (La1-x M-x)(2)Mo2O9-delta where M = Sr2+ or Ba2+ and x = 0.05 and 0.10, respectively. In addition, the electrical conductivities of some of the typical compositions investigated in the present study were measured as a function of temperature by means of the ac impedance technique. The suppression of the phase transition in La2Mo2O9 by the alkaline-earth dopants was verified by differential thermal analysis of the samples. (C) 2003 Elsevier Ltd. All rights reserved.