Electromechanical properties of fine-grain, 0.7 Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.3PbTiO/sub 3/ ceramics

A fine grain, relaxor-based piezoelectric ceramic 0.7 Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.3PbTiO/sub 3/ (PMN-30% PT) has been investigated, which was fabricated using the columbite precursor method. The complete set of electromechanical properties of the piezoceramic at room temperature is determined using a combination of ultrasonic and resonance techniques. This fine-grain ceramic (grain size /spl les/ 2.5 /spl mu/m) exhibits ultra-high dielectric permittivity (/spl epsi//sub 33//sup T/ //spl epsi//sub 0/ /spl sim/ 7000) and a high coupling coefficient k/sub 33/ (= 0.78). Ultrasonic spectroscopy was used to measure the dispersion of the phase velocity and attenuation for the longitudinal wave propagating in the poling direction. Lower attenuation and smaller velocity dispersion were observed compared to modified Pb(Zr/sub x/Ti/sub 1-x/)O/sub 3/ (PZT-5H) ceramics. The measurement results show that this fine-grain PMN-30% PT ceramic is a very good material for making ultrasonic array transducers.