Controllable Preparation Of Textured BT-based Lead-free Piezoelectric Ceramic And The Mechanism Of Enhancing Piezoelectric Performance

Piezoelectric ceramics are a kind of functional material which can convert mechanical energy and electrical energy to each other.Due to their special functionality,piezoelectric ceramics are used in various aspects of daily life and industrial production,such as sound converters,sonars,and transducers.However,because the currently widely used piezoelectric materials are mainly lead-based materials,and lead is easily volatile during use,thereby causing pollution to the environment,so the lead-free piezoelectric ceramics has become a research hotspot for relevant researchers.This article is based on the research of lead-free piezoelectric ceramics,and explores the effects of doping modification and texturing processes on BT-based lead-free piezoelectric ceramics.The research contents are as follows:（1）The effects of the doping of Sb₂O₃ and Sb_0.5Li_0.5Ti O₃ on the phase structure,microstructure,piezoelectric properties,dielectric properties,etc.of Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃ ceramics were studied respectively,and it was found that the introduction of Sb₂O₃ or Sb_0.5Li_0.5Ti O₃ could improve the electrical properties of Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃ ceramics,and the optimal piezoelectric properties(d₃₃=520～562 p C/N)were obtained in（1-x）Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃-x Sb₂O₃（x=0.15 mol.%）and（1-x）Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃-x Sb_0.5Li_0.5Ti O₃（x=0.3 mol.%）system ceramics.And the ceramics had a coexistence of rhombohedral-orthorhombic-tetragonal phases,the grain sizes also became significantly larger,and the surfaces had no obvious holes.This demonstrated that the doping of Sb₂O₃ or Sb_0.5Li_0.5Ti O₃ has adjusted the phase structure of Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃ ceramics to enhance their electrical properties.（2）After adjusting the phase structure of Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃ ceramics by doping Sb₂O₃ or Sb_0.5Li_0.5Ti O₃ and determining the optimal composition,the next step was to prepare platelike Ba Ti O₃ template for the textured BT-based ceramics.In this article,the three-step molten salt methods（the third step utilized the topological chemical reaction）and the layered structure of the Aurivillius compound(Bi₂O₂²⁺[A_n-1B_nO_3n+1]^2-)were used,the platelike precursor Bi₄Ti₃O₁₂,Ba Bi₄Ti₄O₁₅,and Ba Ti O₃ were prepared.In this process,these products and its micro-morphology were determined by XRD and SEM,respectively.（3）The above（1-x）Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃-x Sb₂O₃（x=0.15 mol.%）system was selected,and the ceramic powder slurry was regulated and prepared.And then the platelike Ba Ti O₃ template was oriented in the casting belt by a casting machine,next,the BT-based textured ceramics were successfully synthesize through the processes of cutting,laminating,isostatic pressing,sintering,etc.The XRD diffraction pattern revealed that the prepared textured ceramics had an obvious<001>orientation.It was found that the piezoelectric properties of the（1-x）Ba_0.93Ca_0.07Ti_0.92Sn_0.08O₃-x Sb₂O₃textured ceramics were positively correlated with the texture degree.And when the sintering temperature was 1400℃,the texture degree reached up to the maximum value and the corresponding piezoelectric constant also reached up to the maximum value（194 p C/N）.