| Popis: |
0.7BiFeO3-0.3BaTiO3+0.35%(mole fraction, the same below)MnO2+x%LiF piezoelectric ceramics(BF-BT-MN-xLF) were synthesized via a solid state reaction process. The phase composition, microstructure, ferroelectric and piezoelectric properties of BF-BT-MN-xLF ceramics were measured by XRD, SEM, ferroelectric test system and precision impedance analyzer. The results indicate that LiF doping enhances lattice distortion, promotes sintering and grain growth, as well as the temperature stability of piezoelectric performance. The orientation of the composite defect dipoles produced by the inequivalent substitution of Li+ and F- for A/B site, lags behind the changes in the electric field, and consequently brings about a clamping hysteresis loop. Meanwhile, the investigation on the depolarization behavior and Curie temperature for BF-BT-MN-xLF ceramics reveals that both Curie temperature Tc and depolarization temperature Td increase remarkably, and Tc and Td increase from 500 ℃ and 410 ℃(x=0) to 550 ℃ and 505 ℃(x=0.50), respectively. When the doping amount of LiF is 0.50%, the ceramics sintered at 860-1020 ℃, maintain excellent piezoelectric activity with a high d33 value of 176-202 pC/N. The ceramics with x=0.50 sintered at 960 ℃ show the optimum piezoelectric properties: d33=202 pC/N, kp=34%, Tc≈550 ℃, Td1≈505 ℃. |
