Thermal stability and application limits of LiNb_1-xTa_xO₃ solid solutions

The focus topic of this subproject is the influence of lithium stoichiometry on the high-temperature stability of LNT solid solutions with different Nb/Ta ratios, as well as their application limits. It is well-known that both edge components of the Li(Nb,Ta)O₃ system - LiNbO₃ and LiTaO₃ - grow congruently with about 48.4 mol% Li₂O. However, the stoichiometric Li/Ta or Li/Nb ratio of 1:1 can be achieved, for example, by the vapor transport equilibration (VTE) process. LiNbO₃ crystals with stoichiometric composition generally show better electromechanical properties at high temperatures compared to the congruent crystals. Although, no data on the influence of lithium stoichiometry on the stability of the LNT solid solutions are currently available in the literature, this information is crucial for high-temperature application of LNT. Another important focus of the subproject is the behavior and stability of domain walls at high temperatures and the determination of the poling properties depending on stoichiometry and crystal quality.

• Adjustment of the lithium or oxygen stoichiometry in LNT crystals
• Study of the kinetics of Li₂O in- and outdiffusion as a function of temperature, Li₂O vapor pressure, oxygen partial pressure, and Nb/Ta ratio.
• Determination of the stability of the material parameters in harsh environments as a function of time
• Investigation of the stability of the domain structures

Dr. Yuriy Suhak
Dr. Éva Tichy-Rács

www.iept.tu-clausthal.de/arbeitsgruppen/hochtemperatur-sensorik