FTIR Spectroscopy to Monitor Impurities and Impurity-Interactions in sillenite Crystals

摘要

High reolution (0.04 cm~-1) absorption spectroscopy is applied at 9 K to study the role played on the vibrational spectra by impurities (Im), as Si~4+, Ge~4+, P~5+, and S~6+, in Bi_12SiO_20 (BSO), Bi_12GeO_20 (BGO), and Bi~12TiO_20 (BTO) sillenite single crystals. Up to three-phonon transitions (overtones of the F mode and com- bination of F and A modes) are detected for the impurities in ImO_4 tetrahedra. Weak anharmonicity effects are monitored. The presence of additional Im impurities modify the lines due to a) the stretching of OH, typical of the undoped material, and b) the multi-phonon transitions either of the intrinsic MeO_4 (Me = Si, Ge, and Ti) and of the ImO_4 tetrahedra. New bands are monitored due to the Im-OH interaction.