TRANSPARENT OXYFLUORIDE GLASS-CERAMIC COMPOSITION AND PROCESS FOR MAKING

摘要

A new transparent glass ceramic composition includes an oxide component, a rare earth component, a halide component, and a substantially pure earth rare earth-halide (e.g., REF3) crystal component. The essential composition (in respective mole % amounts) of the new material is: SiO2 (0-80); GeO2 (0-80); Na2O (0-25); K2O (0-25); Rb2O (0-25); Cs2O (0-25); Al2O3 (0-40); Ga2O3(0-40); RE2F6(0 < RE2F6 < 18); PbO (0-15); RO (0-25); ZnO (0-10); ZrO2 (0-2); TiO2 (0-2); Nb2O5(0-10); Ta2O5 (0-10); P2O5 (0-5); B2O3 (0-15); As2O3 (0-10); Sb2O3 (0-10) and XCln (0-5), where RO is at least one of BaO, CaO, SnO and MgO; XCln is a chlorine containing component such as NaCl, LaCl3, AlCl3, or NH4Cl; with (SiO2 + GeO2) (40-80); (Na2O + K2O + Rb2O + Cs2O)(2-25); and (Al2O3 + Ga2O3)(10-40), where RE is one or more, alone or in combination, of Y<3+>, La<3+>, Ce<3+>, Pr<3+>, Nd<3+>, Sm<3+>, Eu<3+>, Gd<3+>, Tb<3+>, Dy<3+>, Ho<3+>, Er<3+>, Tm<3+>, Yb<3+>, and Lu<3+>. In an aspect of this embodiment, the amount of RE2F6 is selected according to the formula: RE2F6 = (K)(R/r)<3> (Al2O3 + Ga2O3 - R2O) 2, where R is one of Na, K, Rb and Cs; 0.7; and r is the radius of RE<3+>. A method for making the new material is also disclosed and includes preparing an oxyfluoride glass containing rare earth ions by a conventional melting method and subjecting the glass to a heat treatment (ceramming), thereby precipitating preferentially fluoride fine crystals containing a large amount of rare earth ions.