Mechanical and dielectric relaxation in neodymium-modified bismuth titanate ceramics

The internal friction (IF) and Youngʹs modulus of Bi3.15Nd0.85Ti3O12 (BNT) ceramics were measured using the reed vibration method in the temperature range from 300 to 750 K at kHz frequencies. One high IF peak (P1) associated with a modulus defect appeared around 453 K. This peak is related to the migration of oxygen vacancies among those unequal oxygen positions in the lattice of the ceramics, which makes it possible to determine the concentration of oxygen vacancies by the peak height. Another peak (P2) appeared around 532 K, which is far below the Curie point (around 890 K), and was attributed to the interaction between oxygen vacancies and 90° domain walls. These results could be helpful to the understanding of the fatigue mechanisms in ferroelectric materials.