Structural and diffuse reflectance study of Ca1−xCoxMO4 (M = W, Mo)

• Precipitation method stabilizes Ca1−xCoxWO4 (x = 0.1–0.3, up to 0.5 for Mo).
• In combustion method, pure phase is obtained with x = 0.1 only.
• Precipitation method yields lavender/blue colored microballs of Ca0.9Co0.1W/MoO4.
• Combustion method yields dispersed particles of grey color.

Precipitation and combustion routes have been followed in the synthesis of Co substituted scheelite phases of the formula Ca1−xCoxMO4 (M = W, Mo). Phase analysis by powder XRD techniques indicated that precipitation method resulted in pure tetragonal scheelite phase formation in the case of compositions Ca1−xCoxMO4 (x = 0.1, 0.2, 0.3) and Ca1-xCoxMO4 (x = 0.1, 0.2, 0.5). While in combustion method, pure tetragonal structure phase was obtained only for the composition with x = 0.1 in both the cases. As evidenced from the SEM analysis that the precipitation method lead to the formation of microballs and the combustion route yielded powder of dispersed particles in the case of Ca0.9Co0.1WO4 and Ca0.9Co0.1MoO4. Similarly, the method of synthesis influenced the color of the above two phases. The colorimetric data revealed the difference in the color hues of the phases with increase in cobalt content in both W and Mo series.

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