Improving Synthetic Method Of PMN-PT And Synthesizing Transparent Ceramics Yb:YAG

The complex perovskite lead magnesium niobate–lead titanate, (1-x)Pb(Mg_1/3Nb_2/3)O₃– xPbTiO₃ (PMN-PT),is a kind of composite structrue between Pb(Mg_1/3Nb_2/3)O₃ and PbTiO3. The Curie point of Pb(Mg_1/3Nb_2/3)O₃(PMN) is nearly -17℃,and nearly this temperature,it is cubic phase.Among PMN-PT,with the development of PT,the structure transforms from cubic to tetragonal,and there is morphotropic phase boundary(MPB) when the content of PT is 32-35mol%. Now,PMN-PT have gained a lot of interest as potential candidates for dielectric and piezoelectric devices,and widely used as multilayer capacitors, electrostrictive actuators, sensors and many other electronic and microelectromechanical devices.However,the frequent problem in the preparation of PMNT ceramics is the formation of unwanted lead-deficient cubic pyrochlore phases over a wide temperature range from 600 to 1400℃via the conventional mixed-oxide method.Swartz and Shrout first succeeded in eliminating the pyrochlore phase by developing the two-stage columbite method. Pyrochlore phase results from the reaction between Nb₂O₅ and PbO. The columbite method avoids this undesirable situation reacting previously all of the niobium with magnesium, resulting in MgNb₂O₆ (MN) columbite phase. This method gives better reproducibility for stoichiometric PMNT which is 100% perovskite phase.Many other routes have been developed for the synthesis of the pure PMNT system,such as molten salt method,sol-sel route to synthesize 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃. Mechanochemical process, low-temperature reactive sintering of 0.65PMN-0.35PT .But there are various shortcomings in all the method above.For example,the starting materials of sol-sel route to 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ is are very sensitive and can not be used widely.So it will pollute the environment. Mechanochemical process is very time consuming and requires high energy mills. Low-temperature reaction required high quality of starting materials which is nanometer level,so it is unfit for mass production.We have recently developed a one-stage method to prepare perovskite PMNT.This method shows the advantage to use cheap chemicals and a simple experimental procedure,so it is suitable for manufacture on a large scale.The reason why this one-stage method could avoid pyrochlore phases was also systematically investigated and discussed.And trying to synthesize the PMN-PT power with the method of microwave-hydrothermal .And synthesized the transparent ceramics Y3Al5O12(YAG for short) and a series of Yb:YAG that the content of Yb3+ is different. Testing the transmittance and absorbance of transparent ceramics with UV-VIS-NIR spectrophotometer.And test the fluorescence spectrum and fluorescence lifetime of transparent ceramics with fluorescence spectrophotometer(Jobin Yvon,SPEX Fluorolog-3).