Novel 1-3 (K, Na)NbO3-based ceramic/epoxy composites with large thickness-mode electromechanical coupling coefficient and good temperature stability

The 1-3 piezoelectric composites are an important type of artificial functional materials for ultrasonic transducers. Currently, there are increasingly strong demands to replace the lead-containing materials. Excellent 1-3 0.96(K0.48Na0.52) (Nb0.96Sb0.04)O-3-0.03BaZrO(3)-0.01(Bi0.50Na0.50)ZrO3 ceramic/epoxy (abbreviated hereafter as KNNS-0.03BZ-0.01BNZ/epoxy) piezoelectric composites were prepared by a modified dice-and-fill technique. Compared to the monolithic KNNS-0.03BZ-0.01BNZ ceramic, the developed composites possess much larger electromechanical coupling coefficient k(t) of 0.54-0.67 and piezoelectric voltage coefficient g(33) of 64-91 x 10(-3) Vm/N. In addition, these composites also possess other favorable properties such as low values of acoustic impedance Z of 6.9-13.4 Mrayl, dielectric coefficient epsilon(33) of 130-400 and mechanical quality factor Q(m )of 1.3-4. More importantly, k(t) is weakly temperature-dependence in the common usage temperature range between -30 degrees C and 100 degrees C. The result indicates that the 1-3 KNNS-0.03BZ-0.01BNZ/epoxy piezoelectric composites have a great potential for high-frequency ultrasonic transducers.