The Pr 3+ and Tb 3+ ground state locations in compounds obtained from thermoluminescence and intervalence charge transfer studies

Abstract

The location of the lanthanide ground states with respect to the host valence band or to the vacuum level always follow characteristic zigzag patterns with the number of electrons q in the 4f orbital. The patterns that are used today evolved over the years by combining experimental data from different techniques, and they are in first approximation independent on the type of compound. Here we will demonstrate that the ground state locations for Pr 3+ and Tb 3+ in the currently used pattern for trivalent lanthanides appear, when inspected on the ± 0.1 eV accuracy level, not consistent with two independent sets of experimental data. One set is from data on the intervalence charge transfer (IVCT) from Pr 3+ and Tb 3+ to the conduction band (CB) observed in luminescence excitation spectra. The other set is from the release of holes from Pr 4+ and Tb 4+ to the valence band observed in thermoluminescence (TL). In addition to the inconsistency, TL based evidence for a slight compound dependence in the characteristic zigzag patterns is found.