Synthesis and Characterization of the Pb5(PxAs1-xO4)3Cl Solid Solutions

A series of the Pb₅(P_xAs_1-xO₄)₃Cl solid solutions were directly prepared through aqueous precipitation method. The results of the elemental analysis, XRD, FT-IR and SEM characterization have confirmed the forming of the mimetite/pyromorphite solid solutions. The XRD analysis indicated that the end-member components of the solid solutions were well matched respectively to card #01-080-2103 for mimetite and #00-019-0701 for pyromorphite, and their corresponding unit cell parameters. In FT-IR spectra, the stretching vibrational absorption band of AsO₄^3- appeared around 788.71-820.00 cm^-1 (γ₃), and the bending vibration absorption band was also visible at 418.00 cm-1 (γ₄). In addition, no vibrations of AsO₄^3- appeared at 1407.82 cm^-1, 1563.44 cm^-1 and 1733.26 cm^-1. There was a clear water peak of pyromorphite appeared at 3440.62 cm^-1 and the antisymmetric stretching peak of PO₄^3- appeared around 979.50-1050.05 cm^-1 (γ₃) and the symmetrical peak appeared around 540.08-575.53 cm^-1 (γ₄). Observed by SEM, the shape of crystals changed gradually from the fibrous, needle-like to the granular solid block as PO₄^3- in the solids increased.