| Sr Ca Bi4Ti5O18(SCBT) ceramics used to manufacture piezoelectric devices under high temperature due to their high Curie temperature, large anisotropy of electromeehanical coupling coefficient, high mechanical quality factor, good temperature stability and low leakage current. In this paper, the modifications of SCBT ceramics were carried out by ion substitution and oxide additive doping. The main results are listed below:1. Bismuth layer structured lead free piezoelectric ceramics in the system Sr Ca Bi4-xEuxTi5O18(x = 0, 0.02, 0.04, 0.06) and Sr Ca Bi4-xHoxTi5O18(x = 0, 0.02, 0.04, 0.06) have been prepared through the conventional solid-state reaction method and the microstructure, ferroelectric properties and piezoelectric properties were studied. It was found that the phase structures of both Eu3+-doped and Ho3+-doped the ceramics are pure bismuth-layered structural. The Eu3+-doping to SCBT ceramics restrained the grain growth. In addition, the piezoelectric constant d33 could be improved at the same time. The ceramics with x = 0.02 exhibited optimum properties Tc = 427 oC, d33 = 20 p C/N. The Ho3+-doped SCBT ceramics remarkably promoted the grain growth and improved the electricity constant d33. For Ho3+-doped SCBT ceramics, the ceramics exhibited optimum properties at x = 0.04, d33 = 20 p C/N, Pr = 5 μC/cm2.2. Bismuth layer-structured Sr1-xCaxNa0.5Bi4.5Ti5O18(x = 0.0,0. 25,0.5,0.75,1.0) lead- free piezoelectric ceramics were prepared by solid-state reaction and the phase structure, microstructure, ferroelectric properties and piezoelectric properties were investigated. Bismuth layer structured lead free piezoelectric ceramics Sr1-xCaxNa0.5Bi4.5Ti5O18+1 wt.% Ce O2(x = 0.0,0. 25,0.5,0.75,1.0) were prepared and the Ca2+-doping to SNBT ceramics caused a remarkably promoted grain growth and improved the Curie temperature. The effects of Ca2+ on the properties of the SCBT ceramics were investigated after Ce O2 doping. It was found that Ce O2 did not destroy the phase structure. The Ca2+-doping to SNBT ceramics caused the obvious lattice distortion. c/a of crystal lattices had increasing trend with the addition of Ca2+, the piezoelectric constant d33 could be improved at the same time. The ceramics exhibited the optimum properties with Tc = 604 oC, Pr = 6.3 μC/cm2, d33 = 31 p C/N at x = 0.25.3. Bismuth layer-structured lead free piezoelectric ceramics in the system Sr Na0.5Bi4.5Ti5O18+xwt.% Ce O2(x = 0, 0.1, 0.2, 0.3, 0.4) and Sr0.5Ca0.5Na0.5Bi4.5Ti5O18+x wt.% Ce O2(x = 0, 0.25, 0.5, 0.75)(SCNBT) were prepared by solid-state reaction and the effect of Ce O2 on the microstructure and electrical properties of the ceramics have been investigated. The result shows that Ce O2 did not destroy the crystal structure, and all samples had a single phase of bismuth oxide layer structure. It was found that there were not obvious changes in Curie temperature of the ceramics with the doping of Ce O2, and all samples had high Curie points(Tc≥560 oC). The dielectric constant decreased gradually with the increase of Ce O2 contents, while the dielectric loss increased firstly and then decreased. In SNBT ceramics, the ceramics exhibited the best properties with Tc = 567 oC, d33 = 29 p C/N, tanδ = 0.015 at x = 0.3. In addition, after annealing at 500 oC, this component ceramic sample’s d33 was still over 22 p C/N. The Ce-doping to SCNBT ceramics caused a remarkably promoted grain growth and improved electricity properties. In SCNBT ceramics, the ceramics exhibited the optimum properties with Tc = 587 oC, tanδ = 0.66%, d33 = 27 p C/N at x = 0.25. |
PDF Full Text Request