| Abstract: | The modified PMnN-PZTbased piezoelectric ceramics of composition Pb0.99Ca0.01 [(Mn1/3Nb2/3)x − (1 − x)(ZryTi1−y)]O3 (0.02 ≦ x ≦ 0.07, 0.47 ≦ y ≦ 0.54) were synthesized by B-siteoxideprecursormethod (BO method) and conventional mixed oxidemethod (MO method). The morphotropic phase boundary (MPB) was adjusted by varying the Zr ratio to compromise the balance between the piezoelectric properties and the temperature stability of static capacitance. The influence of PMnN content on the microstructure, electrical, temperature stability and mechanical properties of the samples synthesized using these two methods were investigated and compared. Results showed that the samples synthesized using the BO method not only lowered the sintering temperature (from 1260 °C to 1150 °C) without adding any sintering aids but also exhibited piezoelectric properties, temperature stability of resonance frequency (TCF) and elastic stiffness coefficient superior to those of MO-type piezoelectric ceramics. Experimental results showed that the bulk density (g/cm3), dielectric loss, Kt, Kp, d33, Qm, (×1010 N/m2), and TCF (ppm/°C) of BO-type ceramics were 7.78, 0.0022, 0.5, 0.63, 345, 1450, 14.65, and 85 compared to those of MO-type ceramics (i.e., corresponding values of 7.65, 0.0025, 0.48, 0.58, 280, 1400, 14.54, and 105) with optimum composition of x = 0.04. The obvious improvement is due to the fine-grain microstructure and chemical homogeneity. In addition, two types of narrow-band therapeutictransducers were fabricated and compared. According to the experimental results, the PMnN-PZTbased piezoelectric ceramics using the BO method are found to be suitable for in ultrasonic therapeutictransducer applications. |
