Thermoluminescent Formation of Cr2+ in Magnesium Oxide

Abstract

In undoped crystals of MgO, x irradiation converts a large fraction of Cr³⁺ in octahedral symmetry to Cr²⁺. Heating such crystals until a blue thermoluminescence has been observed causes further reduction. Usually 95% or more of the Cr³⁺ is converted by the combined treatments. However, in Cr‐doped MgO one is able to reduce only a small fraction of the octahedral chromium to Cr²⁺. The Cr²⁺ is reconverted to Cr³⁺ by heating. ESR measurements show that in the same temperature interval nearly all of the Fe¹⁺ formed on x irradiation has disappeared. The source of electrons acquired by Cr³⁺ thus appears to be the Fe¹⁺ ions. The thermoluminescence is ascribed to the Cr³⁺‐electron interaction, as suggested by Hansler and Segelken.