School of Environmental Science and Management, Independent University^* Department of Chemistry, University of Dhaka, Bangladesh^** Institute of Mineralogy, University of Hannover, Germany^***
○KALPANA RANI DEY^* Dr. Altaf Hussain^** Claus H. Ruscher^***

In the present investigation powder samples of Li_xMo_yW_1-yO₃ (x = 0.1, 0.4, and y = 0.02 0.4) and Na_xMo_yW_1-yO₃ (x = 0.6 and y = 0.05 0.25) have been prepared by solid state reaction in evacuated silica tubes with synthesis temperature 700°C. From X-ray powder diffraction pattern of Li_0.1Mo_yW_1-yO₃ system, it is observed that with increasing Mo content the proportion of PTB_tetr decreases and a phase of orthorhombic symmetry increases with a small amount of impure phase Li₂W₄O₁₃. This X-ray result is supported by IR absorption spectra of the samples. Whereas, in the system Li_0.4Mo_yW_1-yO₃ the proportion of PTB_Cubic phase reduces with increasing molybdenum content. In presence of small amount of Mo, a Li₂W₂O₇ type phase is formed along with PTB_Cubic phase.
From the X-ray powder diffraction patterns of Na_0.6Mo_yW_1-yO₃ system, a PTB_Cubic phase is observed with y 0.1 . However, for y > 0.1 an extra phase of Na₂Mo₂O₇ is also observed along with PTB_Cubic phase.