Atmospheric Pressure Sintering Preparation And Electrical Properties Of Relaxed Ferroelectric PMN-PT Transparent Ceramics

The relaxor ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) materials have been widely investigated for their potential applications in multilayer capacitor, actuator, electro-optical modulator, ultrasonic transducer and infrared detector because of their excellent dielectric, piezoelectric, electro-optic, electrostrictive and pyroelectric properties. The 0.88PMN-0.12PT powders were prepared by ball-milling and sol-gel method using Nb2O5, MgO, PbO, TiO2, La2O3 and Nb2O5-H2O, Pb(NO3)2, Mg(NO3)2·6H2O, Ti(C4H9O)4 as raw materials, respectively. After shaped by dry-pressing or isostatic cool pressing,0.88PMN-0.12PT transparent ceramics were fabricated by conventional sintering. We compared the microstructure difference of PMN-PT prepared by ball-milling and sol-gel method. The influences of sintering temperature, temperature-holding time and content of La-doping on microstructures, transparency and electric properties of PMN-PT based transparent ceramics were discussed. The microstructures and electric properties of high transparent 0.88PMN-0.12PT based ceramics were investigated.Experimentally, the PMN-PT powders prepared by ball-milling and sol-gel method are all perovskite phase. The average grain diameter of the powders from planetary ball-milling is largest than others and the average grain diameter of the powders from sol-gel is smallest. The sintering temperature of PMN-PT ceramics fabricated using powders from planetary ball-milling is highest than others and the average grain diameter of it is largest, while the sintering temperature of PMN-PT ceramics fabricated using powders from sol-gel is lowest and the average grain diameter of it is smallest.The density and transparency of PMN-PT ceramics increased with the sintering going up and temperature-holding time prolonged within a certain range in conventional sintering method. The average grain size, dielectric and ferroelectric properties, Curie temperature Tc, piezoelectric constants and leakage-current density J of the ferroelectric ceramics decrease with increasing La doping content.The transparency of 0.88PMN-0.12PT based ceramic is high as 63% @1550 nm at 1.2 mm. The pure perovskite phase and dense microstructure are observed. However, the average size and density of the ceramics with La-doping are larger than the ceramics without La-doping. The grain boundaries are clear and thin as approximate 1.5 nm as showed in TEM of high transparent PMN-PT based ceramics.