Actinide and rare earth ions in single crystals of ThO 2: Preparation, EPR studies and related problems

Abstract

Actinide and RE ions in ThO 2 single crystals have been studied by means of EPR spectroscopy. Samples were prepared by high temperature solution growth using Pb 2V 2O 7 as flux. In both 0.1% and 1% neptunium doped samples, X-band spectra do not show evidence of Np 4+ resonances down to 3 K; however, the spectra of Er 3+, Yb 3+ and Gd 3+ in cubic sites have been recorded. Moreover, Pu 3+ resonances, together with the ΔM ≠ ± 1 Gd 3+ transitions, have been identified in the sample with lower neptunium concentration. Dy 3+ 0.1% doped ThO 2 crystals show both cubic and trigonal spectra, with a well-resolved hyperfine structure due to the odd isotopes. Analysis of this structure for the observed cubic transition allows us to indicate the role of the nuclear electric quadrupole transition.