Phase transition,microstructure, and dielectric properties of Li/Ta/Sb co-doped (K,Na)NbO3 lead-free ceramics |
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Authors: | Shaohua Qian Kongjun ZhuXuming Pang Jinsong LiuJinhao Qiu Jianzhou Du |
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Affiliation: | State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China |
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Abstract: | Li/Ta/Sb co-doped lead-free (K0.4425Na0.52Li0.0375)(Nb0.93−xTaxSb0.07)O3 (abbreviated KNLNSTx) piezoelectric ceramics, with Ta-doping ratio of x ranging from 0.0275 to 0.0675, were synthesized using the conventional solid-state reaction method at the sintering temperature of 1130 °C. The effects of Ta content on the microstructure, dielectric properties, and phase transition behavior of the prepared ceramics were systematically investigated. The X-ray diffraction results show that all KNLNSTx ceramics formed a secondary phase, which is assigned to the tetragonal tungsten-bronze type (TTB) structure phase, and showed a phase transition from an orthorhombic symmetry to a tetragonal symmetry across a composition region of 0.0375<x<0.0475. The grain shape and size that correspond to the phase structure transformations can be clearly observed in the scanning electron microscopy images. As x increased to 0.0475, the KNLNST0.0475 ceramics changed from orthorhombic to tetragonal structure and showed excellent piezoelectric properties of d33=313 pC/N, kp=47%, and εr=1825. By contrast, samples of x=0.0375 with orthorhombic symmetry exhibited poor piezoelectric properties, with d33=200 pC/N and εr=1015. These results indicate that phase structure is vital in the piezoelectric properties of KNN lead-free ceramics. |
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Keywords: | C Dielectric properties Lead-free ceramics Microstructure Phase transition |
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