Formation and transition of the phases in the Pb-Cr-O system

We used HCl and NH3 gases to adjust the pH value of the suspension prepared by mixing the Pb(Ac)2 and K2CrO4 aqueous solutions, and found the structure, morphology and size of the initial precipitates changed at room temperature. In the acid condition, when the ratio of [Pb2+]/[CrO42−] was 1:1, 1:5 or 1:10, the initial orthorhombic PbCrO4 precipitates would translate to the monoclinic PbCrO4. And the aspect ratio of the obtained particles increased with a decrease in the ratio of [Pb2+]/[CrO42−]. In the basic condition, with the increase in the concentration of the hydroxyl ions, the products converted from the orthorhombic PbCrO4 to the monoclinic Pb2CrO5. The phenomena and results provide the information of the phase formation and transition in the Pb-Cr-O system, and enrich the field of the crystal growth.