Fabrication BNT-BKT-BT Textured Ceramics By Reactive Templated Grain Growth (RTGG)

Piezoelectric ceramics are widely used in sensors, actuators and energy storageapplications. For environmental consideration, the development of high performancelead-free piezoelectric cermics has become a problem demanding prompt solution. Inthis paper, reactive templated grain growth (RTGG) are studied to fabricate [001]pctextured (1-x-y)Bi0.5Na0.5TiO3-yBi0.5K0.5TiO3-xBaTiO3(BNBK) ceramics. Thetape-casting process, the evolution of texture, the effects of template grain growth andthe structure and electrical properties are studied.In this work, random-oriented BNT based ceramics are papared by conventionalsolid state reaction method include BNT-BKT, BNT-BKT-BT and Li-modifiedBNBK(BNBK-Li). The microstructure, phase structure and electrical properties arestudied. The ternary0.85BNT-0.11BKT-0.04BT morphotropic composition showshigh piezoelectric constant and electromechanical coupling factors (d33=189pC/N,kp=0.25). The modified Li has effects both on lattice distortion and liquid phasesintering. For BNBK-Li, the sample with x=0.07exhibited the highest properties:d33=230pC/N, kp=0.30.BNT-BKT-BT (BNBK) lead-free piezoelectric ceramics with extensive [001]texture were fabricated by the reactive-templated grain growth method usinganisotropic Bi4Ti3O12particles as templates. The formation of texture include in-situtopochemical reaction process(800℃) and epitaxial growth process(>1000℃). Thetextured BNBK ceramics using BIT as seeds are well oriented, giving a Lotgeringfactor of0.6. The piezoelectric response is enhanced by the grain orientation, and thepiezoelectric constant (d33) of the textured ceramics sintered at1170oC attained avalue of254pC/N, which is41%higher than random ceramics (180pC/N).Also, several key points in RTGG process are discussed. Using BaTiO3as Basource is helpful to keep the morphology of the templates during the in-situtopochemical reaction process. It is easy to enhance effects-oriented by increase thecontent of templates. Liquid phase supplied by excess Bi2O3facilitate the orientedgrains grew utilizing a dissolution-deposition mechanism. However, using BNTinstead of Bi2O3, Na2CO3and TiO2as matrix powder is not a good way to enhanceepitaxial growth, because the minute BNT grains offer crystal nucleus for matrixpowders leading to a high growth rate of matrix grains.