Controlled atmosphere process for altering the nonstoichiometry of crystalline members

摘要

The nonstoichiometry of a crystalline member is altered by promoting conditions of vapor phase equilibrium between the member and a slotted crucible in which it is placed. The slotted crucible comprises material sharing a common vapor species with the crystalline member and provides an atmosphere of substantially constant thermodynamic activity with respect to the shared vapor phase upon isothermal heating of the member and crucible. In one embodiment, by achieving a partial vapor phase equilibration between a transparent crystalline member and such a crucible both the magnitude and profile of the refractive index of the member near its surfaces is modified in a controlled member.