Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2

Abstract

The optical spectra of Yb 3+ ions in congruent, Sr 0.6 Ba 0.4 Nb 2 O 6 ͑SBN͒ crystals have been systematically investigated in a broad temperature range ͑10-420 K͒. 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 K͒ 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.

Synthesis and the luminescent properties of CdNb2O6 oxides by sol–gel process

“…The synthesis and electro-optical properties of metal niobates have been intensively investigated during the past half century [1][2][3]. Additionally, niobates are known as interesting photoactive host materials, and the luminescent properties of LiNbO 3 [4], KNbO 3 [5], LnNbO 4 (Ln = La, Gd, and Y) [6,7] and KNb 3 O 8 [8] have been studied extensively.…”

Absorption spectroscopy and energy levels of rare earth impurity centres in Srx Ba1–xNb2O6 crystals

“…The results for the detected absorption lines are presented in Fig. 3c, which shows their different polarization properties, which change very little with temperature even above T c [11]. We compared these experimental data with the polarization selection rules for certain symmetry groups derived from group-theory analysis for the electron transitions between the Kramers states.…”

“…The absorption spectra of Er 3+ and Tm 3+ demonstrate more broadened and overlapping spectral lines corresponding to the transition between 4f-states of 4f 11 and of 4f 12 electronic configurations of these ions. The additional broadening of spectral lines could be related with a higher degree of lattice disorder as well as with higher multiplicity of Er 3+ and Tm 3+ impurity centres in the crystal lattice of SBN.…”

“…There is clearly shown that Tm 3+ is very sensitive to the phase transition of SBN. This dependence is due to many site occupation of Tm 3+ ion like Yb 3+ in SBN [11]. In addition to that, an analysis about site occupation of rare earth ions is given.…”

“…2 and Table 1. Taking into account this fact, the detection of 3 instead of 4 transitions (originating from the lowest sublevel of 3+ can be further decomposed into a number of subbands (for instance 3) corresponding presumably to slightly different optical centres of Ce 3+ in the SBN crystal lattice [11]. This decomposition is changing only slightly up to room temperature, does not depend on the Ce 3+ concentration available and does not depend on light polarization.…”