(Received August 6, 1971)
The values of mechanical quality factor Qm are determined for lead zirconate titanate ceramics containing various oxides as impurities in various amounts. Impurities are found to be classified into two groups with respect to the change of Qm values, viz., (1) Qm decreases in the presence of impurities (e. g. Nb2O5), (2) Qm increases in the presence of minor additions (e.g. Cr2O3). The values of Qm are found to increase when both the amount of space charge and specific resistivity increase. This seems to be caused by the suppression of domain wall motion resulting from the prevention of space charge migration. An empirical formula is obtained for Qm as a function of the reduced amount of space charge and specific resistivity.