Nephelauxetic effect of the hydride ligand in Sr(2)LiSiO(4)H as a host material for rare-earth-activated phosphors

Strontium lithium orthosilicate hydride Sr(2)LiSiO(4)H was synthesized by the reaction of Sr(2)SiO(4) with LiH at 700 °C in a H(2) rich atmosphere. Rietveld refinement of the neutron powder diffraction pattern revealed that Sr(2)LiSiO(4)H is isostructural to Sr(2)LiSiO(4)F (space group P2(1)/m) and its channel-like structure preferentially accommodates H(−) ions over F(−) ions. In addition, Sr(2)LiSiO(4)H is stable in air and its Eu(2+)-doped analog exhibits yellow photoluminescence with an emission band at 544 nm and a broad excitation band ranging from 250 to 450 nm. These bands were observed in the longer wavelength region when compared with those displayed by Sr(2)LiSiO(4)F:Eu(2+). The red shift, which is induced by H(−) substitution, is consistent with the constrained density functional theory calculations, predicting the photo-excitation and emission energies of 4f–5d transitions. The present study reports the synthesis of stable oxyhydrides acting as phosphor hosts for rare earth ions. The phosphor hosts exhibit large nephelauxetic effects owing to the presence of H(−) ligands.