Mechanical loss and elastic modulus associated with phase transitions of barium titanate ceramics

Abstract

The internal friction ( Q −1) and elastic modulus ( E) were measured vs. temperature (100 < T < 450 K) for rectangular plate specimens of BaTiO 3 driven electrostatically in flexural vibration at resonance frequencies between 2 and 4 kHz. The Q −1( T) and E( T) curves exhibit the following three phase transitions in BaTiO 3: rhombohedral to orthorhombic ( T R-O), orthorhombic to tetragonal ( T O-T) and tetragonal to cubic ( T Curie). Each phase transition induces either a very narrow internal friction peak or a discontinuous change in Q −1 and a very sharp anomaly of the elastic modulus. Moreover, two other internal friction peaks are located below the phase transition temperature. These peaks seem to be associated with the motion of domain walls. The secondary peaks are not observed on undoped ceramics sintered at low temperature. The influence of dopants such as Nb and Co results in the attenuation of internal friction and the smoothing of elastic modulus anomalies.