Study On The Toughening Of The High-power Lead Zirconate Titanate Piezoelectric Ceramics

In order to address the poor toughness of the high-power devices, the toughening of a binary high-power PZT piezoelectric ceramic system has been systematically explored via doping of YSZ or rare earth elements, mixing powders calcined at different temperatures, complex doping, etc. The phase structure and morphology of the ceramic samples were examined by x-ray diffraction (XRD) and scanning electron microscopy (SEM), while the mechanical and electrical properties of the samples were evaluated by Vick’s hardness and fracture toughness tests, and piezoelectric and dielectric measurements, respectively. First of all, the high-power piezoelectric ceramic materials with excellent performance have been obtained. The formula is as follows: Pbo.95Sro.o5(Zr0.525Tio.475)03+1.1mol%CaFeO5/2+0.3mol%Fe2O3+0.2mol%Li2CO3+0.1mol%MgO.The ceramics achieved optimum electric properties:d33=259pC/N, Qm=702, Kp=54.0%, ε33T/ε0=1038, and tan δ=0.0029.It was observed that the YSZ addition results in enhancement of the density, Vick’s hardness (HV) and fracture toughness (KIC) of the ceramics. The maximum value of obtained is1.506MPam1/2at0.5wt%YSZ addition. While the KIC is increased by15.9%, decline of the electrical performance of this sample is not obvious compared with ceramics without YSZ doping.It was revealed that the rare-earth (Nd, Dy, Yb) addition generally enhances the KIC, d33, Kp, ε33T/ε0but decreases the Qm of the samples. The rare-earth doped ceramics generally have a small grain size and high density. Each rare-earth element plays a certain role in alteration of the ceramics toughness. For Nd-doped ceramics, the maximum value of KIC obtained is1.485MPa-m1/2at0.3wt%Nd2O3addition; the KIC is increased by14.0%compared with the undoped ceramic. For Dy-doped ceramics, the maximum value of KIC obtained is1.483MPa·m1/2at0.2wt%Dy2O3addition; the KIC is increased by13.8%compared with the undoped ceramic. For Yb-doped ceramics, the maximum value of KIC obtained is1.503MPa-m1/2at0.2wt%Yb2O3addition; the KIC is increased by15.3% compared with the undoped ceramic.The mechanical properties of the ceramic samples have been improved through mixing the powders calcined at different temperatures thus having different grains size. When adding8wt%ceramic powders calcined at1050℃to the powders calcined at850℃, the final ceramic achieved optimum mechanical properties with the Kic of1.506MPa·m1/2, which is increased by15.9%compared with the ceramic sintered under normal conditions. On the other hand, the piezoelectric properties of the ceramic are not affected much.It was further revealed that the ceramic toughness can be enhanced to some extent by a synergistic combination of YSZ doping, Yb2O3doping, and introducing powders calcined at different temperatures. The maximum value of Kic obtained is1.52MPa-m1/2for the sample that was doped with Yb2O3and incorporated powders calcined at higher temperature, and the KIc is increased by16.6%compared with the ceramic prepared under normal conditions.The PZT ceramic materials developed in this work through different means of toughening possess both good electrical properties and superior mechanical properties, showing great potential in the applications of high-power piezoelectric devices.