High Sm Concentrations Research Articles

New Complex Fluorides EuMgF4, SmMgF4, SrMgF4, and Their Solid Solutions: Photoluminescence and Energy Transfer

Three previously unknown compounds, , , and , and solid solutions, have been prepared by a method involving the use of Mg metal as a reducing agent for the Eu and Sm. Both and appear to be excited via a 4f → 5d transition (broad band). emits a bright blue under 356 nm peak excitation, the emission peak being at 437 nm. has sharp line emission assigned to transitions. In solid solutions , maximum efficiency is found at and the efficiency of is only about 5% less, adding to the small group of known “stoichiometric phosphors.” This is correlated with magnetic measurements which show little or no exchange interaction between neighboring rare earth ions. The magnetic behavior of the Sm2+ ion in suggests the possibility of mixing of the and states of the ground state manifold, owing to strong acentric crystal fields. In solid solutions, there is remarkable energy transfer from Eu2+ to Sm2+, the Eu2+ emission being barely detected at and completely absent at higher Sm concentrations. Evidence for both radiative and nonradiative transfer was found, but the nonradiative mechanism appears to predominate.