Effect of preparation methodology on the colour and the NIR reflectance of nickel doped manganese pyrophosphate

Abstract

Nickel doped Mn2P2O7 pigments of the formula NixMn2-xP2O7 (x = 0.0.5, 1.0, 1.5, 2.0) were prepared by precipitation and hydrothermal methods and characterized by PXRD, FT-IR, UV-DRS and SEM - EDX. The colour parameters were studied using CIE-LAB parameters. It is noteworthy that when x = 0 reddish pink colour was observed in precipitation method whereas in hydrothermal method pale pink colour was noticed. The colour hue change from pink to yellow was observed when x value is increased from 0 to 2.0. Well defined morphology was obtained in hydrothermal method, whereas precipitation method leads to the formation of irregular morphology. NIR Solar reflectance (R*) was found to be 79% for x = 0 prepared by hydrothermal method but by precipitation method it was reduced to 65%. Increased lightness (L*) value (less intense) was noticed for the all samples prepared by hydrothermal method compared to precipitation method (more intense). A yellow pigment which is free of chromium, cadmium and lead was obtained.