CHARACTERIZATION OF DEFECTS IN TUNGSTEN SAMPLES INTERESTED IN PFM STUDIES USING POSITRON ANNIHILATION AND PHOTOLUMINESCENCE SPECTROSCOPY

Abstract

The defect structure of four pure tungsten samples is investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL) and positron annihilation spectroscopy (PAS) techniques before and after annealing. The results of the SEM and XRD analyses show that the grain size is increased up to 43.3[Formula: see text][Formula: see text]m, and their growth in the (2 0 0) orientation occurs at 1673[Formula: see text]K. Also, the smooth of the peaks at 1673[Formula: see text]K in the PL test demonstrates the increase of the size of defects of the sample. Moreover, the results of the PAS indicate a decrease in the concentration of defects and an increase in their size at 1673[Formula: see text]K, which confirms the results obtained from the PL measurement. The collected results from the four examination techniques are in close agreement with each other and reveal that w ith the increase in the annealing temperature of tungsten samples, a gradual coalescence of the defects would happen to lead to an increase in their size and hence a reduction in their number as well as preferred grain growth in the (2 0 0) orientation and virtually perfect recrystallization of the samples at higher temperatures.