Zn₂SiO₄ crystal growth from molten solutions fluxed with Pb₂ZnSi₂O₇ and fluorides

Abstract

Single crystals of Zn2SiO4 (willemite) in the form of hexagonal prisms several millimeters in size are grown between 1300 and 960°C by the cooling (1°C/h) of molten solutions composed of 5 Zn2SiO4 + 3 Pb2ZnSi2O7. Supplying most of the zinc as the fluoride improves crystal size and quality as do Mn and especially As. Chemical analyses and buoyancy density measurements indicate a nonstoichiometric Zn1.96Si1.04O4.04 crystal formula. Divalent Mn substitutes significantly, but not completely, for Zn to form solid solutions of the well-known and efficient green willemite phosphor. Arsenic, which increases the persistence of phosphorescence (afterglow), is incorporated into willemite crystals to a lesser degree than Mn, i.e., As has a low segregation coefficient. Little if any Pb is soluble in willemite grown this way. © 1982.