THE ELECTRICAL-CONDUCTIVITY OF SAPPHIRE IRRADIATED AT 550-700-DEGREES-C WITH AN APPLIED ELECTRIC-FIELD OF 1 KV CM/

Sapphire has been irradiated at 550, 600, 650 and 700 degrees C using 10 MeV protons to damage doses of > 10(-3) displacements per atom (dpa ). An electric field of 1 kV/cm was applied across the sample during i rradiation. The irradiations were interrupted at intervals and the tem perature dependence of electrical conductivity measured. The results s howed that for irradiation temperature > 600 degrees C the conductivit y decreased with increasing damage dose. Irradiation at 600 degrees C produced more complex changes in which the conductivity depended upon both the damage dose and the thermal history of the sample. The conduc tivity initially decreased after a dose of 10(-4) dpa but began to inc rease again after 10(-3) dpa. However, holding at 500 degrees C overni ght annealed out the increase and the conductivity fell back to the ea rlier decreasing trend line. Irradiation at 550 degrees C produced an order of magnitude increase in conductivity although, as at 600 degree s C, there was still a tendency for the increased conductivity to anne al out.