Low-frequency internal friction study on modified lead metaniobate ceramics

Six Q(-1) peaks in freshly-worked PbNb2O6 ceramics are observed by low-freq uency internal friction measurement so far as we know for the first time. P -1, P-2, and P-4 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. P-3 is a widened Debye relaxation peak in nature. T he activation energy and pre-exponential factor are about 1.01 eV and 2.5 x 10(-12) s, respectively. This peak is attributed to the interaction of dom ain walls and oxygen vacancies. P-6 is corresponded with the paraelectric a nd ferroelectric phase transition. P-5, appearing near T-c, is thought to b e caused by the viscous movement of the domain walls.