LOW-FREQUENCY INTERNAL FRICTION STUDY ON MODIFIED LEAD METANIOBATE CERAMICS

Six Q^-1 peaks in freshly-worked PbNb₂O₆ ceramics are observed by low-frequency internal friction measurement so far as we know for the first time. P₁, P₂, and P₄ appear at the first heating process with remarkable shear modulus anomalies. But they are not observed during the cooling process or in the well-annealed samples. Those peaks are considered to be related with the working processes. P₃ is a widened Debye relaxation peak in nature. The activation energy and pre-exponential factor are about 1.01 eV and 2.5×10^-12 s, respectively. This peak is attributed to the interaction of domain walls and oxygen vacancies. P₆ is corresponded with the paraelectric and ferroelectric phase transition. P₅, appearing near T_c, is thought to be caused by the viscous movement of the domain walls.