Preparation Of PMN-PT Textured Ceramics

As a new-style functional material with promising applications in many fields, relaxor ferroelectric xPb(Mg_1/3Nb_2/3)O₃- (1-x)PbTiO3(PMN-PT) single crystals could perform higher dielectric, piezoelectric and electrostrictive properties. (001) PMN-PT textured polycrystalline piezoelectric materials are expected to provide improved properties compared to untextured ceramics, and low processing cost compared to single crystals. In this paper, (001) platelike SrTiO₃ and SrBi₄Ti₄O₁5 were selected as template particles, highly textured PMN-PT ceramics have been prepared by templated grain growth with directional powder, tape casting and hot pressing. Combing with d₃3 test and density measure, the composion, structure and properties of the PMN-PT textured ceramics have been studied systematically.In order to array the platelike crystallites along one particular direction, tape casting was adopted to prepare the green tape. The influence of the properties of powders and the content of the organic additives of the quality of the green tape was researched, and the optimal composition of the tape casting slurries was determined according to different powders through tape casting experiment.Several layers of the green tape were laminated and sintered into ceramics by hot pressing and anneal sintering in common pressure. The result maked that the density of texture ceramics was good, the electrical properties of the oriented sample appeared anisotropy, and the texture fracture was about 63% in (001) direction. The piezoelectric constant which achieved 480pc/N in 10 vol% SrTiO3 was higher than that of random samples.The glass frits of PbO, B₂O₃ and ZnO were added into the matrix and analysed the influence on the properties of texture ceramics with different content of frit. The dielectric contant and loss tangent were raised and the piezoelectric properties were descended with the content of frits increasing. But d₃3 of the texture ceramics was achieved 568pc/N with 1 wt% PbO. This indicated that the appropriate frit can improve the piezoelectric property of ceramics in right content.On the basis of the above studies, PMN-PT texture ceramics was also fabricated with (001) platelike SrBi₄Ti₄O₁5 as template particles. The result showed that thepiezoelectric constant could obtain 390pc/N in 10 vol% SrBi₄Ti₄O₁5 and the properties would increase with the improvement of preparation technique. All of the experiment conclusions made clear that, for PMN-PT texture ceramics, the 10 vol% content of template particles was better.