Characterization of mechanical loss in piezoelectric materials using temperature and vibration measurements

In this research, a unique approach for characterizing mechanical loss in piezoelectric materials is developed. Instead of characterizing mechanical loss through electrical measurements, thermal and mechanical measurements are used. A comprehensive heat transfer model has been developed to describe the temperature rise due to heat generation in piezoelectric materials in resonance conditions. Using this model, along with experimental temperature and vibration measurements, the mechanical quality factor can be calculated. Advantages of this method over electrical impedance methods include high sensitivity to change in losses due to precise temperature and vibration measurements and evaluation of losses from a single frequency (versus a frequency sweep). This method has been applied to a hard PZT ceramic at several frequencies near its fundamental resonance at a tip vibration velocity of 300 mm/s RMS. In these high power conditions, the standard deviation of the mechanical quality factor resulting from the impedance data was 15%, while those resulting from the new method are less than 2.5%. The results from the impedance measurements using a constant vibration velocity sweep agree with the magnitude of the quality factor calculated from new method, giving evidence to its validity.