The Preparation Of PMN-PT-based Ferroelectric Ceramics And Their Electrical And Luminescent Properties

The relaxor ferroelectrics?1-x?Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃?abbreviated as PMN-PT?has excellent ferroelectric,piezoelectric and electro-optic properties.Transparent PMN-PT ceramics are very suitable for developing electro-optic switch and other devices,which have attractive prospects for applications in Optical Communications.Meanwhile,rare-earth doped PMN-PT transparent ceramics are good photoluminescence materials.They have wide applications in optical sensor and 3D display and can be used for making electronic controlled photoluminescence devices and multi-functional optical devices.We synthesized PMN-PT powders through a columbite precursor method and then prepared La-doped 0.88PMN-0.12PT transparent electro-optic ceramics and Er-doped0.67PMN-0.33PT luminescent ceramics by oxygen atmosphere sintering and hot-press sintering.In this paper,the preparation process of PMN-PT transparent ceramics is introduced,then the effects of pre-sintering temperature and rare-earth-ions doping amount on the electrical,optical and photoluminescence properties of the transparent ceramics are discussed.The main results and conclusions are as follows:1.Transparent 0.88PMN-0.12PT ceramics with different La-doping amount?La=0.5?1.0?1.5?2.0 mol%?were sintered.All the ceramics belong to pure perovskite phase and are very dense.Their cross sections show mainly transgranular fracture.The ceramics are highly transparent.The transmittance of the ceramic with La content of 1 mol%is about 65%at 632 nm and reach 70%in the near infrared region,close to the theoretical limit value.With increasing la-doping content,both the residual polarization and coercive field of transparent 0.88PMN-0.12PT ceramics decrease,their hysteresis P-E loops become thinner and lean,and the temperature dependence of their dielectric constant gradually widen,indicating that the relaxation characteristics of the ceramics are monotonously enhanced.2.The microstructure and properties of transparent 0.88PMN-0.12PT ferroelectric ceramics sintered at 1220?,1230?,1240?and 1250?were compared when other preparation conditions remained unchanged.It was found that the average grain size of the ceramics increases and transgranular fracture occurs more frequently with increasing pre-sintering temperature.The 0.88PMN-0.12PT ceramics which were pre-sintered at1250?exhibit the highest transmittance.Both the hysteresis-loop shape and dielectric constant of the ceramics do not significantly depend on the pre-sintering temperature.3.Ferroelectric 0.67PMN-0.33 PT ceramics with different Er doping amount?Er = 0?0.5?1.0?1.5 mol%?were prepared.All the ceramics belong to a single perovskite phase with high density.The ceramics containing Er of 1.5 mol%show the most rectanglar hysteresis loop,the largest values of both their residual polarization and coercive field.Their piezoelectric coefficient d₃₃ is as high as 700 pC/N.Er-doped 0.67PMN-0.33PT ceramics not only show down-conversion luminescence,but also exhibit up-conversion luminescence at 980 nm excitation wavelength.