Stabilizing the scheelite AWO4 (A = Ba, Sr, Ca) phase materials by combustion followed by heat treatment

The nanocrystalline AWO(4) (A = Ba, Sr, and Ca) materials were obtained by combustion followed by annealing at 800 degrees C for 3 h by using the nitrate salts of A = Ba, Sr, and Ca and other required raw materials. The XRD, TG-DTA, FT-IR, Raman, UV-Vis, FESEM, and EDX results of the AWO(4) series are presented in this article. The as-prepared combustion products show mixed phases, whereas the annealed samples yield pure scheelite phase, AWO(4), crystallized in a tetragonal, I41/a (88) structure. The refined lattice parameters of the scheelite phases significantly vary with the difference in the ionic radii of the alkaline earth metals (A). The band gap (E-g) values obtained from Tauc plots are found as 5.63, 5.3, and 5.12 eV for A = Ba, Sr, and Ca, respectively, in the AWO(4) series.

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This study successfully synthesized nanocrystalline AWO (4) (A = Ba, Sr, and Ca) materials via combustion followed by annealing. The characterization results showed that the annealed samples exhibited pure scheelite phase and the lattice parameters of scheelite phases varied significantly with the difference in the ionic radii of the alkaline earth metals (A). The band gap (E-g) values in the AWO (4) series were found to be 5.63, 5.3, and 5.12 eV for A = Ba, Sr, and Ca, respectively.