Solution combustion synthesis: a straightforward route for the preparation of chromium-doped lanthanum aluminate, LaAl1-xCrxO3, pink red pigments

The high exothermicity of the combustion reactions in the La(NO3)3-Al(NO3)3-Cr(NO3)3-urea-glycine system allows the obtaining of LaAl1-xCrxO3 (x = 0.05) pink red pigments directly from the combustion reaction, without any additional annealing. The Al3+ by Cr3+ partial substitution causes a decrease in the combustion temperature from 1721 °C to 1563 °C. The presence of 2 % CaF2 mineralizer causes colour intensification and red hue increase. The LaAl1-xCrxO3 crystallites size varies between 51 nm and 71 nm and the BET specific surface area varies between 3.0 m2/g and 7.3 m2/g. The characteristics of the obtained pigments are correlated with the combustion gases release rate, which in turn depends on the combustion temperature, the resulting volume of gases and the duration of the combustion reactions. Pigment testing has shown that it dissolves in the enamel melt but can be used to obtain water-based acrylic paints.