Dopant host and process for production thereof

Abstract

Provided is a dopant host with which the amount of B2O3 volatilized is unlikely to decrease over time and that has good B2O3 volatilizing ability for a long period of time. The dopant host has a laminate that includes a boron component volatilization layer containing 30 to 60 mol % of SiO2, 10 to 30 mol % of Al2O3, 15 to 50 mol % of B2O3, and 2 to 15 mol % of RO (R is an alkaline earth metal) and a heat resistant layer containing 8 to 40 mol % of SiO2, 40 to 85 mol % of Al2O3, 5 to 30 mol % of B2O3, and 0.5 to 7 mol % of RO (R is an alkaline earth metal). At least one outermost layer of the laminate is composed of the boron component volatilization layer. The laminate further includes the boron component volatilization layer inside the laminate. The boron component volatilization layer constituting at least one outermost layer of the laminate has a B2O3 content lower than the B2O3 content in the boron component volatilization layer inside the laminate.

Dependencies are inferred from the claim text.