Preparation of Yellow Pigment of Nickel Pyrophosphate System

The yellow pigment of α-Ni2P2O7 system was prepared by calcining the compound of Na4NiPO4 systems, synthesized by wet method from Ni2+ and (NH4) 2HPO4 in aqueous solution. Three compounds, NH4NilP4·H2O, Na4NiPO4·6H2O and Ni3 (PO4) 2·8 H2O were obtained according to the mixing molar ratios of Ni2+ and (NH4) 2HPO4 and aging temperatures. Among these three compounds, Na4NiPO4·6H2O was excellent giving fine colored α-Ni2P2O7 after calcination. In particular, the calcined product at 1,150°C of NH4NiPO4·6 H2O, prepared from Ni2+ and (NH4) 2HPO4 in molar ratio of 1 : 10 and aged at 60°C, showed the best vivid yellow color.