ANELASTIC BEHAVIOR OF BARIUM-TITANATE-BASED CERAMIC MATERIALS

The internal friction (Q(-1)) and Young's modulus (E) of BaTiO3-based ceramics were measured vs temperature from -100 degrees C to 150 degrees C. Rectangular bars of high-density (96 to 99 pet) materials were driven electrostatically in flexural vibration at a resonance frequency of about 3 kHz, at maximum strain levels of about 10(-6). The curves of Q(-1)(T) and E(T) allow the study of the following three phase transformations: tetragonal to cubic (about 130 degrees C in pure material), orthorhombic to tetragonal (about 0 degrees C in pure material), and rhombohedral to orthorhombic (about -80 degrees C in pure material). Internal friction and modulus data were obtained on pure material and on materials doped with niobium and cobalt to give semiconducting and insulating X7R behavior. Permittivity, dielectric loss, and microstructure data are given and used to aid interpretation of the mechanical measurement data.