Electronic Processes in Zinc Fluoride and in the Manganese-Activated Zinc Fluoride Phosphor

Abstract

Measurements have been made of the temperature‐dependence of electrical conductivity and thermal e.m.f. on ZnF₂ and ZnF₂:Mn, and of the Hall coefficient and rectifying power at 25°C on ZnF₂. Both ZnF₂ and ZnF₂:Mn are N‐type impurity semiconductors. The presence of MnF₂ in ZnF₂ decreases the electronic conductivity by a factor of about 10³, indicating a decrease in the concentration of electron donors by oxidation. A marked dependence of the temperature variation of conductivity on heat treatment has been observed. Contrary to the simple theory, the absolute values of the thermal e.m.f. increase with temperature. From the Hall coefficient and conductance at 25°C of heat‐treated ZnF₂, a concentration of free electrons of 3×10¹⁶ cm⁻³ and a mean free path of 6.7×10⁻⁸ cm are deduced. ZnF₂ rectifies in the expected direction.