New chromium doped powellite (Cr–CaMoO4) yellow ceramic pigment

A new chromium doped powellite (Cr–CaMoO4) yellow ceramic pigment alternative to yellow of praseodymium-zircon has been synthesised and characterised in order to analyse: (a) the stoichiometry of the solid solution, (b) the effect of the dopant concentration under the pigmenting properties, (c) the effect of the chromium precursor and mineralizers addition, (d) the effect of the synthesis method. The composition CrxCaMo1−xO4x=0.075 using K2Cr2O7 or Cr2O3 as chromium precursors fired at 1000–1100 °C produces a yellow colour, slightly lower in intensity than the commercial praseodymium-zircon yellow pigment in double (1000 °C) or single firing (monoporosa—1080 °C or porcelainized stoneware—1200 °C) ceramic glazes. By a coprecipitation method with ammonia, and firing at 950 °C, the yellow ceramic pigment glazed in a conventional CaO–ZnO–SiO2 glaze (monoporosa glaze, 1080 °C) shows a yellow colour similar to the commercial praseodymium-zircon yellow pigment. However the release and possible mobilization of the Cr (VI) should be controlled in order to get its industrial implementation.