Patent ID: 7547652

Claim:
A composition of vitroceramic type comprising, in mol %: Ge 5-40 Ga <1 S + Se 40-85 Sb + As 4-40 MX 2-25 Ln 0-6 Adjuvant 0-30 in which: M represents at least one alkali metal chosen from Rb, Cs, Na, K and Zn, X represents at least one chlorine, bromine or iodine atom, Ln represents at least one rare earth metal, and Adjuvant represents at least one additive composed of at least one metal and/or at least one metal salt, with the sum of the combination of the molar percentages of the components present in said composition being equal to 100, wherein the composition is a quaternary mixture of germanium in a content varying from 15 to 130 mol %, of antimony in a content varying from 4 to 20 mol %, of selenium in a content varying from 50 to 70 mol % and of CsX, in a content varying from 3 to 15 mol %.