Electrical properties and temperature stability of Li-deficient and near stoichiometric Li(Nb,Ta)O3 solid solutions up to 900 C

It is widely known that the intrinsic properties of LiNbO3, LiTaO3 and, consequently, of Li(Nb,Ta)O3 solid solutions are strongly dependent on lithium stoichiometry. In the current work the electrical properties of Lideficient and near-stoichiometric single crystalline Li(Nb,Ta)O3 are studied as a function of temperature by means of impedance spectroscopy. The preparation of near-stoichiometric samples was performed by Vapor Transport Equilibration technique (VTE). It is shown, that VTE-treated samples generally exhibit lower conductivity, which implies better thermal stability. The latter was examined by the measurement of the electrical conductivity of the samples at 500 & DEG;C in air. After about 330 h of uninterrupted thermal treatment the conductivity of VTE-treated LiNb0.94Ta0.06O3 specimen was found to decrease for about 10%. To compare - the conductivity of congruent LiNbO3 specimen decreased for about 15% after 330 h of annealing at 500 & DEG;C.