Evaluation of the effect of the thermal cycling temperature on the losses in alumina substrates.

Thanks to the dielectric relaxation spectroscopy method we present results of measurements of dielectric losses versus frequency in alumina substrates before and after thermal treatment. This one consists in applying thermal step of negative and positive values. This type of stress corresponds to those encountered in railway applications. The role of thermal cycling is evaluated, and is rather important. Losses are essentially due to polarization, while the effect of conduction phenomena is less important. For the low frequency range, interfacial phenomena are attributed to the polarization. Results are discussed using the Maxwell-Wagners-Sillars law and Havriliak-Negami's model. On the other hand, the electrical field dependence of losses shows not non-linear phenomenon in the range of voltage [0-3.5kV].