Effects of Er³⁺and Yb³⁺doping on non-linear properties of double lithium sulfates

Abstract

The crystalline network that characterizes the family of ferroic materials of the kind of ALiSO4 (A=Na, NH4, K) has a great flexibility, which facilitates the existence of phase transitions and non-linear properties. However, lately, the research has been basically directed to the ionic conductivity these networks present. The work we present here is a part of a research line on the effects of rare earths in non-linear matrixes due to their great technological interest. The study of the structural properties due to the doping of LiNaSO4 with Yb +3 and Er +3 were performed by Palmero et al. (J. Luminic. 128, 2008). The doped compounds showed no important structural differences in relation to the pure ones. Apart from that and for the first time, they observed second harmonic generation (SHG) in all cases. In what refers to LiNH4 SO4, Gonzalez-Silgo et al. (2008. In Press), found two new alpha phase polimorph isotypes of the Li(NH4)1-2X YbXSO4 doped compound, which present SHG. In this work, the Lithium-Potassium sulphate has been analysed using the same procedures and experimental techniques as in previous cases (RX, TG-DTA, DSC and SHG). The structural differences observed in the compounds doped with Yb +3 and Er +3 show some rotation with respect to the pure one. The data obtained from the three sulphates allow us to present a comparative study on the Yb +3 and Er +3 doping effect in relation to their non-linear optical properties in the context of the structure and the temperature behavior. The results are quantitatively discussed in two different ways: using the Bond-Valence Sum (BVS) model and the Abraham-Kurt-Jamienson criterion, which are compared with the model presented by Xue and Zhangs (Phys. B 262, 1999) for non-linear compounds.