| PbNb2O6-based ceramics is a kind of high temperature piezoelectric ceramics. In this study, the PbNb2O6-based piezoelectric ceramics were studied. Effects of the doping of Bi3+, sintering atmosphere, and particle size of precursor powders on structure, dielectric and piezoelectric properties of the PbNb2O6-based ceramics were studied in detail. The main results are as following:(1) (Pb0.985-xBi2x/3La0.01)(Nb0.95Ti0.0625)206 (x = 0,0.01,0.04,0.06,0.1) piezoelectric ceramics were prepared via a conventional solid state reaction method. Effects of the doping of Bi3+ on structure, dielectric and piezoelectric properties of the ceramics were studied in detail. The results show that all ceramics have the pure orthorhombic ferroelectrics phase. The doping of Bi3+ facilitates decreasing the sintering temperature. The Curie temperature decreases with the increase of the Bi3+ amount. For the ceramics with x = 0,0.01,0.04 and 0.06, the values of dielectric constant remain nearly unchanged from room temperature up to approximately 400 ?. The ceramic with x = 0.04 shows high piezoelectric charge constant (d33 = 87 pC/N), mechanical quality factor (Qm = 22.60), low dielectric loss (tan? = 0.024), and high Curie temperature (Tc= 494 ?). The thermal annealing results show that the d33 values of the poled ceramic with x = 0.04 are above 75 pC/N during the temperature range of room temperature and 475 ?.(2) On the basis of the experiment (1), (Pb0.945Bi0.027La0.01)(Nb0.9sTi0.0625)206 was chosen. The ceramics were sintered in the atmospheres of nitrogen (N2) and oxygen (O2), abbreviated as PBLNT/N2 and PBLNT/O2. The ceramics show pure orthorhombic ferroelectrics phase. The atmosphere of O2 facilitates decreasing the sintering temperatures of the ceramics. The lattice parameters of the ceramics are related to the sintering atmospheres. The mean grain size of the ceramics are related to the sintering atmosphere and sintering temperature. The values of dielectric constant remain almost unchanged at temperatures between room temperature and about 400 ? for all ceramics. Compared with the ceramics sintered in N2, the Curie temperature of the ceramics sintered in O2 decreases, while the piezoelectric charge constant of the ceramics sintered in O2 increases. During the temperature range of room temperature and 498 ?, the d33 value of PBLNT/N2 decreases from 74 pC/N to 71 pC/N, while that of PBLNT/O2 decreases from 80 pC/N to 75 pC/N.(3) On the basis of the experiment (1), (Pb0.945Bi0.027La0.01)(Nb0.95Ti0.0625)2O6 (i.e., PBLNT/0.04) was chosen. Precursor powders with different average particle size were obtained by means of different milling methods. The milling methods were high-energy vibration milling (Sample ?) and normal planetary milling (Sample ?). Effects of the particle size of precursor powders on calcination, structure, piezoelectric and dielectric properties of the ceramics were studied in detail. The precursor powders prepared via the high-energy vibration milling show the pure rhombohedral phase after calcining at 725 ?, while the calcination temperature increases to 900 ? to obtain the pure rhombohedral phase for the precursor powders prepared via the normal planetary milling. Sample ? sintered at temperatures from 1170 ? to 1185 ? formed the pure orthorthombic phase, while the sintering temperatures increase to 1180?1190? to obtain the single orthorthombic phase for Sample ?. The anisotropy of the grains in Sample ? was weakened obviously. The dielectric properties of the both samples are similar. The values of dielectric constant remain almost unchanged at temperatures between room temperature and about 400 ?. Sample ? sintered at 1180 ? shows improved piezoelectric charge constant (d33= 87 pC/N), while Sample I shows a lower d33. |
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