Electrical and electromechanical properties of stoichiometric lithium niobate at high-temperatures

Electrical and electromechanical properties of lithium niobate crystals with various compositions from congruent to stoichiometric are analyzed in the temperature range from 500 °C to 900 °C and in the oxygen partial pressure range from 10− 14 bar to 0.2 bar. The total conductivity is found to decrease with increasing lithium concentration while the activation energy of the conductivity increases. The oxygen partial pressure dependence results in a slope of − 0.22 in the plot log(σ) vs. log(pO2). Ionic and electronic conductivity and the lithium diffusion coefficient are determined using this data. The piezoelectric properties of lithium niobate allow the excitation of thickness and shear vibration modes depending on the crystal orientation at temperatures up to 900 °C. For both modes the temperature dependence is observed and the inverse Qf product determined, which represents the loss.