Ion Doping And Texturing Of BT-based Lead-free Piezoelectric Ceramics

Piezoelectric ceramics are widely used in daily life and military components due to their excellent electrical properties and temperature stability.At present,the lead-based piezoelectric ceramics are the most widely used,such as buzzers,sensors,sonar,etc.However,the lead piezoelectric ceramics are harmful to the human health and living environment,which makes the research and application of lead-free piezoelectric ceramics extremely urgent.The paper focuses on improving the performance of BT-based lead-free piezoelectric ceramics by means of ion doping and textured modification,including systematically studying the preparation process of piezoelectric ceramics,the microstructures and the electrical properties.Research results as follows:(1)The(1-x)(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃-x LiTaO₃-0.3mol%GeO₂(0?x?0.5)solid solution ceramics were prepared by conventional ceramic processing route.The effects of Li₂CO₃,Ta₂O₅and GeO₂on the phase structure,microstructure and electrical properties of the ceramics were systematically discussed.It was found that the phase coexistences of R-O-T when x=0.2mol%,which made the ceramics obtain excellent piezoelectric and dielectric properties,e.g.,d₃₃=570 pC/N,k_p=61%,?_r=14887,tan?=0.007.(2)The plate-like BaTiO₃template was prepared by three-steps molten salt method.Including the products of the Bi₄Ti₃O₁₂and BaBi₄Ti₄O₁₅prepared in the first and second steps,and the plate-like BaTiO₃template obtained by topological chemical reaction.In addition,the phase structure and the morphology of the prepared template was analyzed by XRD and SEM.Finally,the BT template with the grain size of 2.98?m and the thickness of 0.4?m was prepared.(3)The BCZT-0.2mol%LT-0.3mol%G-x%BT(0?x?8)textured ceramics were prepared by template grain growth method with the(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃-0.2mol%LiTaO₃-0.3mol%GeO₂system as the matrix powder and BaTiO₃as the template.In addition,the texture degree,phase structure,microstructure and electrical properties of the textured ceramics were analyzed.The results show that the texture degree,dielectric constant and piezoelectric properties of the textured ceramics are achieved at the content of 2%BT template added,which is f₍₀₀₁₎=44.36%,?_r=15606,d₃₃=310 pC/N,k_p=31%.(4)The effects of doping modification and texture modification on the phase structure and electrical properties of the ceramics were compared.It was found that the two modification methods were beneficial to the improvement of electrical properties of ceramics.Among them,the piezoelectric properties of the ceramics are effectively improved by doping modification.Textured modification can effectively improve the dielectric properties of ceramics.However,the piezoelectric properties of the textured ceramics with BT template are slightly inferior to those of the traditional solid-phase piezoelectric ceramics because of the large chemical differences between the template and the matrix and the relatively small grain size of the template.