ゾルーゲル法を用いて作製したGeO_2ガラス中のEr3^<3+>周りの局所構造に関する振動及びXAFSスペクトルによる研究

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Vibrational, Er Z_<III>-edge X-ray absorption fine structure (XAFS), and upconversion fluorescence spectra have been measured for sol-gel derived xEr_2O_3・(100-x)GeO_2 (x= 1-10) glasses. Raman spectra indicated that with increasing the Er2O3 content, the bridging angle of the Ge-O-Ge linkage was distorted and non-bridging oxygen atoms (NBOs) were generated. Infrared absorption spectra of the glasses showed that the amount of the residual OH group increased with increasing the Er_2O_3 content. XAFS analysis showed the argumentation of both the coordination number (N_<Er-O>) and the Debye-Waller factor (σ_<Er-O>) with increasing the Er_2O_3 content. This argumentation is probably due to the coordination of NBOs, OH group, and bridging oxygen atoms (BOs) to the Er^<3+> ion. XAFS analysis for the glasses gives no evidence of clustering of Er^<3+> ions as reported previously. Quenching of Er^<3+> upconversion fluorescence in the glasses with high Er_2O_3 content is considered to be caused mainly by the coordinated OH group.
2004-05-01