Search for new apatite-like pigments: From synthesis to color measurements

Abstract

In the present study, colored compounds with an apatite structure of compositions Sr5(PxVyCrzO4)3F (x + y + z = 1.0) were synthesized using a solid-state method. All compounds, except when z = 0.0, were colored in different shades of green. P5+ and V5+ ions are not coloring ions, so the color varied depending on the amount of Cr5+. A comprehensive analysis of the structures of the newly synthesized ternary solid solutions was conducted, and the crystallographic boundaries of the isomorphous mixture were refined. The reliability factors obtained from the refinement demonstrate that the ternary solid solutions crystallize in a hexagonal symmetry, space group P63/m. The pentavalent P, V, and Cr ions occupied equivalent tetrahedrally coordinated positions in the structure. The bond lengths in the tetrahedral positions are distorted more as the content of the pentavalent ion with a larger radius increases. The conducted comprehensive investigation (crystal structure, infrared spectroscopy, color measurements) of the colored compounds with an apatite mineral structure of compositions Sr5(PxVyCrzO4)3F (x, y, z = 0.0 to 1.0) opens up new possibilities for the development of alternative pigments and expands the application range of pigments based on similar materials.