This paper concludes that the deterioration of the mechanical quality factor Q(m) when operated under high power, can be recovered by externally applying positive DC bias field. Material constants for piezoelectric ceramics are generally characterized under low-power conditions. However, high-power properties deviate significantly from the ones measured under low-power conditions (Q(m) degrades by a factor of similar to 2). DC Bias field helps to recover the properties of the ceramic under high-power conditions. The DC bias field of 200V/mm exhibits an almost equivalent opposite change rate to the vibration velocity of 0.1m/s. It is also notable that the piezoelectric loss tan ' can be decreased most effectively under positive DC bias field (1.9% per 100V/mm for the hard PZT and 3.1% per 100V/mm for the soft PZT), in comparison with the elastic or dielectric losses. This report presents a comprehensive analysis on the low- and high-power piezoelectric properties of hard and soft Lead Zirconate Titanates (PZT's) under externally applied DC bias field in the k(31) resonance mode (transverse extensional).