The effect of quenching on the defect structure of calcium fluoride doped with erbium

Abstract

Audio frequency dielectric relaxationmeasurements over the temperature range 5.5–390 K and optical absorption studies at 8 K have been performed on various samples of rare‐earth dopedcalcium fluoride. Erbium was the principal dopant and the studies were carried out for a series of concentrations before and after vacuum anneal at 1125 K followed by a quick quench. Strong effects were observed on all spectra. A similar anneal followed by a slow cool returned the samples to their initial state. It is shown that RI and RII correlate with optical signals associated with the A and B sites of Tallant and Wright. The annealing results are consistent with the identification of these sites as monomer (single rare‐earth) sites of C 4V and C 3V symmetry, respectively. RIV, which has recently been shown to be associated with a dimer (two‐rare earths), correlates with optical signals associated with the C site of Tallant and Wright. This suggests that the dimer exhibits approximately trigonal symmetry. In addition, RIII is found to be associated with optical signals which correlate with the D sites of Tallant and Wright. The annealing results suggest that RIII may be due to a higher order cluster. Finally, the annealing results suggest that RV is associated with a relatively simple site.