Tb(HSO4)(SO4) – A Green Emitting Hydrogensulfate Sulfate with Second Harmonic Generation Response
Recently, sulfates attracted attention as materials for non-linear optical applications. This compound class is extended by Tb(HSO4)(SO4), which is solvothermally synthesised from Tb4O7 and sulfuric acid. The compound crystallises in the non-centrosymmetric space group P21 (Z = 2, a = 665.03(5) pm, b = 659.41(5) pm, c = 680.24(5) pm, β = 104.640(2) °) and is homeotypic with Ni2In. The terbium ions adopt the indium sites and the sulfate and hydrogensulfate anions are situated on the nickel sites. The compound shows green luminescence based on f-f-transitions and the position of the f-d-excitation bands reveal a weak coordination behaviour of the sulfate anions. Tb(HSO4)(SO4) exhibits a second harmonic generation response comparable to KH2PO4 (KDP). Furthermore, the material is characterised by electrostatic calculations, infrared spectroscopy and thermal analysis.