High Temperature Synthesis of Inorganic Pigments in the ZnO-MgO-COO-Al(OH)3-Al System

Bismuth vanadate-based pigments deposited on marshalite are synthesized by the low-temperature combustion reaction method using vanadium oxide V₂O₅ and bismuth salt BiONO₃·H₂O. The quantitative composition of the starting components is calculated from the BiVO₄ -to- marshalite ratio = 1:3. To clarify the pigment, zinc nitrate Zn(NO₃)₂·6H√O and calcium hydroxide Ca(OH)₂ are added. Citric acid is used as an energetic and gas-forming additive. X-ray diffraction analysis (DRON-3M diffractometer, filtered CuKα radiation) showed the formation of a microimpurity such as VO₂ oxide during the synthesis of bismuth vanadate. The phase of the complex Aurivillius-type oxide Bi4V2011 that gives the pigments a beige tint is found along with bismuth vanadate and marshallite during the synthesis of the pigment on a mineral substrate (marshallite). IR spectroscopic analysis (Nicolet 5700 IR Fourier spectrometer) showed that the fixation of bismuth vanadate-based pigment was caused by silanol groups located on the surface of marshalite and the incorporation of VO4 tetrahedra into the surface of marshalite due to the formation of “umbrella-shaped” bonds (Si-O-V). The absorption bands at 1370,2 cm^-1, 1397.0 cm^-1, and 1757.7 cm^-1 indicate the presence of carbonate groups on the surface of the pigment, related to both chemisorbed carbon dioxide CO₂ and carbonate ion CO₃^2-. The dispersion of pigment is determined by the dispersion of marshalite, which acts as a mineral substrate. The pigment is stable up to 750°C; an increase in the treatment temperature leads to its darkening.