Influence of gadolinium concentration on the EMR spectrum of Gd in zircon

Electron magnetic resonance (EMR) spectra of gadolinium-doped zircon (ZrSiO₄) powders have been studied at room temperature for gadolinium concentrations between 0.20 and 1.0 mol%. The results suggest that Gd³⁺ ions occupy substitutional sites in the zircon lattice, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration and that the range of the exchange interaction between Gd³⁺ ions is about 1.17 nm, larger than that of the same ion in other host lattices, such as ceria (CeO₂), strontium oxide (SrO) and calcium oxide (CaO). The fact that the electron magnetic resonance linewidth of the Gd³⁺ ion in polycrystalline zircon increases, regularly and predictably, with Gd concentration, shows that the Gd³⁺ ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of ZrSiO₄.