Metal hydrides exhibit interesting properties as hosts for Eu(II) containing luminescent compounds due to the nephelauxetic effect and the strong ligand field of the hydride anion. In order to elucidate the lattice site symmetry of europium dopants, Q-band and X-band electron paramagnetic resonance (EPR) spectra were collected on LiMH3 : Eu2+ and LiMD3 : Eu2+ (M = Sr, Ba) powders with europium concentrations between 0.0037 and 0.27 mol %. They show well resolved hyperfine splitting in the central part of the spectra due to magnetic electron spin-nuclear spin coupling of 151Eu and 153Eu, and are in good agreement with simulated spectra based upon cubic site symmetry. Spin Hamiltonian parameters were extracted by spectral analysis and are reported. Low intensity rhombic spectra contributions could be assigned to small amounts of MH2 : Eu2+ or the respective deuterides as impurities in the samples. The results of this EPR investigation and size considerations suggest that europium is divalent and occupies the alkaline earth metal (M) positions in LiMH3 : Eu2+ and LiMD3 : Eu2+ (M = Sr, Ba).
The authors would like to thank Andries Meijerink for help with the luminescence measurements and the Deutsche Forschungsgemeinschaft (grants KO 1803/3-1 and KO 1803/7-1) and the Landesgraduiertenförderung Saarland for financial support.
©2015 Walter de Gruyter Berlin/Boston