PHOTOACOUSTIC PHASE-TRANSITION OF THE CERAMIC BATIO3

Photoacoustic signals from the ceramic BaTiO3 are analyzed, as a funct ion of temperature close to structural phase transition from tetragona l to cubic at 110 degrees C. The amplitude of the signals depends on t he changes of the thermoelastic properties in the ceramic with tempera ture. The Curie temperature value for the phase change was reproducibl e and was found to be 109+/-6 degrees C. A comparative analysis of thi s result with the differential thermal analysis and permittivity techn iques is performed. Two changes of sign in the photoacoustic signal ar e observed, associated with the thermal expansion coefficient behavior in this material near the transition. (C) 1998 American Institute of Physics.