New Eu2 + sites in KMgF3:Eu2 + crystal

Abstract

The luminescence properties ofKMgF3:Eu2 + are investigated at different pressures in the temperature range 25–292 K. Five newEu2 + luminescence (NEL) lines due to the transition are identified at 362.49 nm (L1), 362.53 nm (L2), 360.72 nm (L3), 360.15 nm (L4) and 359.59 nm (L5) together with theline at 359.32 nm (L0)which is well known in KMgF3:Eu2 + . The emission lines under excitation at 325 nm show a strong dependence ontemperature. At 25 K the emission spectrum consists of only two sharp lines,L1 andL2. Threeadditional lines (L3, L4 and L5) begin to appear with increasing temperature. With a further increase in temperature from150 to 292 K all the lines disappear except for the single sharp line at 359.32 nm (L0). The zero-phonontransition of line L0 is accompanied by vibronic sidebands. A pressure shift of five NELs is estimated to be about − 0.6 cm − 1 kbar − 1 similarly to theshift of line L0, while the lifetimes of the NELs are about 0.7 ms which is shorter than that (5.2 ms) ofL0 at 80 K. The new luminescence lines are attributed to theEu2 + ions occupyingthe K + sites withfluorine vacancy (F − center) complexes.