| As the awareness of environmental protection and sustainable development strategies has been deeply rooted among the people, the research and development of environment-friendly lead-free piezoelectric ceramics has become an emergent issue of great significance.In this paper, the (1-x)(0.84Bi0.5Na0.5TiO3-0.16Bi0.5K0.5TiO3)-xBiAlO3(BNT-BKT-BA) ceramics were prepared by conventional solid-state reaction method, and the (1-x)(0.84Bi0.5Na0.5TiO3-0.16Bi0.5K0.5TiO3)-xBiFeO3(BNT-BKT-BF) ceramics were prepared by sol-gel method. The synthesis and preparation, structure characteristics and electric properties of the materials were investigated. The relation between the piezoelectric properties and the composition and structure was also studied. The dielectric relaxation feature and phase transition of the ceramics have been established in terms of experimental results.For BNT-BKT-BA lead-free ceramics system: the grain size increases and the size distribution gets uniform, producing a homogeneous and dense microstructure with the increasing BiAlO3 content. When x=0.02, the sample exhibits optimum electrical properties (d33 = 128 pC/N, kp = 0.205, Qm = 91.8 and tanδ= 6.2%). The temperature dependence of the dielectric constant and dissipation factor from the room temperature to 600°C was studied, and then the dielectric relaxation feature for the ceramics has been discussed.For BNT-BKT-BF lead-free ceramics system: it was found that the morphotropic phase boundary (MPB) with rhombohedral and tetragonal co-existed crystalline structure for the ceramics lies in x=0.01. The addition of BiFeO3 causes a promoted grain growth and densification. The piezoelectric constant d33, electromechanical coupling factor kp and mechanical quality factor Qm of the ceramics show an obvious improvement by a small amount of BiFeO3 substitution. Around the MPB composition, the sample exhibits optimal electrical properties (d33 = 125 pC/N, kp = 0.244, Qm = 114 and tanδ= 4.8%). |
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