| Due to their excellent piezoelectric properties, lead-containing ceramics such as lead zirconate titanate based solid solutions with perovskite structure have long been the matrials of choice for piezoelectric sensor and actuator applications. However, environmental issues call for the use of nonhazardous substances for device fabrication, making the study of lead-free piezoceramics imperative. Among them, sodium bismuth titanate is considered to be one promising candidate ascribed to the strong room-temperature ferroelectric and high Curie temperature. To decrease the electric conductivity and also further improve the electromechanical responses, sintering process and dopant of BNT based solid solutions were studied in this paper.0.94Bi0.5Na0.5Ti O3-0.06 Ba Ti O3 lead-free piezoceramics were prepared by conventional solid state synthesis. The effects of sintering temperature on the phase structure, microstructure and electric properties have been systematically investigated. It is verified that the relaxor behavior of BNBT6 ceramics is enhanced with increasing sintering temperature, and the indicators of diffuesness were 1.696, 1.787, 1.897, 1.965, respectively. The ceramics were dense with well-developed microstructure, having relative density as high as 98.4% of the theoretical density at 1100°C, and the excellent properties were also achived: ρ=5.99g/cm3, d33=180p C/N, Pr=38.7μC/cm2, Ec=37k V/cm, kp=0.331, Qm=135, tanδ=0.026.The electric field-induced strain behavious of(1-x)(0.94Bi0.5Na0.5Ti O3-0.06 Ba Ti O3)-x Li Nb O3(0≤x≤0.06) ceramics have been systematically studied in terms of both compositions and temperature. For the phase coexistence of ferroelectric and relaxor phase at room temperature with x=0.025, the gaint strain as high as 0.6% and normalized strain d33*=857 pm/V were achieved. Near this composition, high strain of 0.55% with normalized strain d33*=785 pm/V for x=0.02 was also dicovered, along with a good piezoelectric of d33=245 p C/N. The temperature dependent strain behavior for the composition of x = 0.01, 0.02, 0.04 and 0.05 were inspected over a wide temperature range. For x=0.01 and 0.02, the high strain values from 344 pm/V, 617 pm/V to 912 pm/V, 836 pm/V were obtained when the temperature heated up to the vicinity of ferroelectric-relaxor temperature TF-R, respectively. For x=0.04 and 0.05, the strain value nearly unchanged with increasing temperature as TF-R fell below room temperature, and the electrostrictive coefficient was basically 0.02m4C-2.0.96(Bi0.5Na0.5)Ti O3-(0.04-x)Ba Ti O3-x Li Nb O3(0≤x≤0.04) piezoceramics with pure perovskite structure were prepared by solid-state reaction method. The phase structure, density, and electric properties have been systematically studied. All ceramics were well-sintered and dense, having relative density of higher than 97% of the theoretical density. It is noted that the ceramics were relaxor ferroelectrics, and the indicators of diffuesness were 1.907, 1.844, 1.746, 1.593, 1.708, respectively. It is demonstrated that the ceramics have a phase transition from rhombohedral to tetragonal at 0.02≤x≤0.03, and high electric properties were obtained with x=0.03: d33=124p C/N, Pr=37.9μC/cm2, Ps=43μC/cm2, Ec=47k V/cm, εr=694, tanδ=0.045。... |
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