Aurivillius-type structure ceramics are considered to be good candidates for use as high-temperature piezoelectrics. To this aim, it is essential to know the resonance characteristics in the working temperature range, rather than at room temperature. In this paper, an automatic iterative procedure has been used to characterize the planar resonance mode of ceramics with composition (SrBi2Nb2O9)(0.35)(Bi3TiNbO9)(0.65)(n = 2), processed by recrystallization after hot-pressing of mechanically activated precursors. The appearance of additional resonances at high temperatures is related to the anomalies in the electric characteristics of the ceramics (dielectric permittivity and losses and dc conductivity). These features are most probably associated with the presence of defects. The role of microstructure is discussed. The range of temperature in which these ceramics can be used as high-temperature piezoelectrics is established. (C) 2004 The Electrochemical Society.