Thermal hysteresis in the luminescence of Yb3+ ions in Sr0.6Ba0.4Nb2O6

The optical spectra of Yb(3+) ions in congruent, Sr(0.6)Ba(0.4)Nb(2)O(6) (SBN) crystals have been systematically investigated in a broad temperature range (10-420 K). Laser site selective low temperature fluorescence spectra have shown that Yb(3+) ions enter in four different cationic lattice sites. A thermal hysteresis in both bandwidth and luminescence intensity of Yb(3+) ions has been detected in the temperature range (300-400 K) around the ferro to paraelectric phase transition. This behavior has been explained as a result of the local structural modifications that take place around the Yb(3+) ions when the crystal becomes nonpolar, which affect in a different way the luminescence of Yb(3+) ions located in the different sites. Off-congruent SBN crystals activated with Yb(3+) ions have been grown and investigated in order to examine the possibilities of extending the detected hysteretic behavior to other temperature ranges.