Preparation Of Codoped SrTiO₃: Pr³⁺ Materials With Sol-gel Method And Study Of Their Luminescent Mechanism

SrTiO₃∶Pr³⁺ is a typical luminescence material with the pervokite structure sensitized with rare earth ions.When codoped with another metal ions this material exhibits a great enhancement in red luminescence properties.It has become a hot point in the next generation PDP phosphors.In this dissertation,a simple and practical sol-gel method is adopted to prepare SrTiO₃∶Pr³⁺ materials codoped with different metals ions(Li⁺;Mg²⁺;Al³⁺),and the different effects of each codoped ion on the modification of the sample were compared. Meanwhile we set up different models of SrTiO₃∶Pr³⁺ for density functlional theory(DFT) theory research in the mechanism of the luminescence enhancement.The sol-gel method we adopted could partly make the dopant ions incorporate into the SrTiO₃ crystalline structure,but the main phase remained.Powder samples and thin film samples of codoped SrTiO₃∶Pr³⁺ show the same luminescence characters,but the powder samples are with much higher density.Al codoped sample gets the best luminescence enhancement in all the codoped samples,and Mg and Li also cause an small enhancement. All the samples show a proportional increase in 617nm emission spectra according to the 360nm excitation spectra,which indicate that the ions spice and doping concentration cannot affect the main process of photoluminescence.The first principle calculations show that Al codoped model has the stablest structure among the doped models,and the doping behavior change the indirect band gap of SrTiO₃ into direct band gap.Because of Pr³⁺,2 dopant levels emerge in the middle of the bang gap. The Al codoped sample has Fermi level electron DOS most favorable for the 617nm emission. Population and charge density show that the polyhedron constructed with Pr,O and metal ion is key structure for red luminescence.