Study On Optical Properties Of Spinel - Type Magnesium Aluminate - Based Ceramics

With good physical and chemical properties, MgAl₂O₄ ceramics can be used in many areas, such as optical materials, catalysts and refractories. Furthermore, the Ga-doped MgAl₂O₄ ceramics can be used to prepare the scintillator, and MgAl₂O₄ ceramics doped with transition metal are very promising materials for solid-state tunable lasers which emit in visible region. There are no theoretical calculations, however, have studied the optical properties of MgAl₂O₄ doped with Ga, Zn or Cu, nor experiments investigated the photoluminescence spectra of MgAl₂O₄ ceramics doped with Zn or Cu. With significance theoretical meaning and practical value, it is worthy to research the optical properties of MgAl₂O₄ ceramics doped with Ga, Zn or Cu by means of theoretical calculation and experiment.In this thesis, the structural parameters and optical properties of MAl₂O₄ （M= Mg, Zn, Cu）, MgGa₂O₄ and MgAl₂O₄ doped with Ga, Zn or Cu were studied by first-principles calculations, and the photoluminescence properties of Zn or Cu doped MgAl₂O₄ ceramics synthesized by pressureless sintering have been investigated. It is found that the calculated structural parameters and optical properties of MAl₂O₄ （M= Mg, Zn, Cu） and MgGa₂O₄ are in line with literatures; When the doping amount of Ga is less than 25% or the concentration of Cu is less than 12.5%, the doped MgAl₂O₄ will keep normal spinel structure, while the doping amount of Zn has no great influence on the parameters of Zn doped MgAl₂O₄; The band gap of doped MgAl₂O₄ decreases with the increasing doping amount of Ga, Zn or Cu, but all of them are direct bandgap materials; Although the static dielectric constant and refractive index of doped MgAl₂O₄ are gradually increased, they still are transparent in visible region; The pure MgAl₂O₄ and Zn or Cu doped MgAl₂O₄ powders prepared at 900℃ have formed spinel phase; The optimum sintering temperature and time of MgAl₂O₄ ceramic sintered by conventional sintering are 1500℃ and 5h, respectively; The Zn or Cu doped MgAl₂O₄ ceramics sintered 5h at 1500℃ have formed spinel ceramic, and their emission intensities at 470nm increase as the Zn and Cu concentration increases up to 0.3% and 0.5%, respectively; Compared to pure MgAl₂O₄ ceramics, the 650nm emission of Zn or Cu doped MgAl₂O₄ ceramics disappears and their emission intensities at 720nm is smaller; The emission intensities at 720nm of Cu doped MgAl₂O₄ ceramics decreases more than that of Zn doped MgAl₂O₄ ceramics and the 720nm emission of Cu doped MgAl₂O₄ ceramics almost vanishes when Cu doping amount increases up to 1.0%; Mg-vacancy will be compensated by Cu or Zn and then the relaxation channel of emission at 650 nm due to Mg-vacancy color centers will be eliminated and the relaxation channel of emission at 720 nm will decrease.