Synthesis and Characterisation of Mn-doped CaTiO3 Pigments Via the Sol-gel Method: Effect of Substitution Steps on the Pigmentary Properties

Abstract

The CaTi1-xMnxO3 pigments (x = 0, 0.05 and 0.1) were synthesised by the sol-gel process by calcining at high temperatures. The influence of manganese substitution (IV) on the phase composition, particle size distribution, microstructure, diffuse reflectance in the ultraviolet-visible-near infrared regions, colour and thermal stability of CaTi1-xMnxO3 pigments was investigated. The phase composition of CaTiO3 and CaTi0.95Mn0.05O3 demonstrated the formation of a single-phase product of CaTiO3 with an orthorhombic structure at temperatures of 900 °C - 1200 °C. In the case of CaTi0.9Mn0.1O3, the same phase was confirmed only at a temperature of 1200 °C. The powders were applied into an organic binder, with the doped samples displaying colour hues ranging from camel brown via light brown to ochre, whereas the undoped CaTiO3 exhibited a white colour. The particle size of d50 was varied in the range of 2-7 μm, with the formation of agglomerates observed at higher temperatures. The ASTM G173-03 standard was employed to calculate the solar reflectance (R*) within the wavelength range of 280-1650 nm. The R* value for the doped pigments exhibited a range of 35%-47 %, with the calcination temperature influencing this value. Additionally, the pigments demonstrated an excellent thermal resistance up to 1150 °C.