COMPOSITIONAL DEPENDENCE OF UP-CONVERSION LUMINESCENCE OF ER3+ IN ZRF4-BASED GLASSES

As one of the compositional designs for enhancing the unconversion luminescence efficiency or Er3+ in ZrF4-based glasses, the anion substitution effect has been examined in glasses 58ZrF4 · (39-x)BaF2 · xBaX2 · 3 Er(or Eu)F1tx = 0-29 for X = Cl and x = 0-10 for X = Br in batch compositions). Prominent enhancement of upconversion emission intensity was observed on the substitution of Cl for F. The Cl substitution brought about two effects, of which one was an increase in the deviation from inversion symmetry in the F— coordination around Er3+ and the other was an increase in both phonon energy and electron-phonon coupling strength. The former raises the transition probability in the upconversion process, leading to an enhancement of the emission intensity, while the latter increases the multiphonon relaxation in the upconversion process, leading to a reduction of the emission intensity. Due to these antithetical effects on the upconversion process, the upconversion emission intensity of the Cl substituted glasses exhibits a maximum value around the 58ZrF4· 20BaF2· 19BaCl2· 3ErF3 composition. The substitution of small amounts of Cl for F is concluded to be quite effective for enhancing the upconversion efficiency of ZrF4-based glasses. © 1993 Academic Press, Inc.