Effect Of Rare Earth On The Structure And Photoelectric Properties Of Gallium Oxide And Ga₂O₃-Based Alloys

Luminescent materials are usually composed of host materials,activators,and sensitizers,etc.Rare earth ions are usually used for activators for their excellent luminescent properties which are attributed to their unique electronic structure.Wide bandgap semiconductors are good host materials because luminescence efficiency would be enhanced and temperature quenching effects can be improved by increasing the bandgap of hosts.With a wide band gap（～4.9 e V）,gallium oxide is one of the ideal matrix materials for rare earth ion doping due to its good thermal and chemical stability.Rare earth doped nanometer luminescent materials have advantages in the fields of thermal imaging,anti-counterfeiting,and biological imaging for their high surface activity,easy coating,and good biocompatibility.However,there is little research on rare earth ions doped gallium oxide nano luminescent material exceptβ-Ga2O3:Eu³⁺.Therefore,it is necessary to develop relative research works.The main contents in this thesis are summarized as follows:1.The theoretical research on Tb³⁺-doped and Gd³⁺-doped monoclinic gallium oxide.The stability,crystal structures,band structures,and density of states ofβ-Ga2O3:Tb³⁺andβ-Ga2O3:Gd³⁺were investigated by CASTEP module which is based on DFT.The results are as follows:（1）Ga1 atoms tend to be replaced by Tb³⁺and Gd³⁺compared with Ga2 atoms inβ-Ga₂O₃ to form substitutional doping systemsβ-Ga₂O₃:Tb³⁺andβ-Ga₂O₃:Gd³⁺.（2）The lattice parameters and cell volume ofβ-Ga₂O₃:Tb³⁺andβ-Ga₂O₃:Gd³⁺are greater than that ofβ-Ga₂O₃ as a result of the radius of Tb³⁺and Gd³⁺are larger than that of Ga³⁺.（3）The bandgap ofβ-Ga₂O₃:Tb³⁺decreased with increasing doping concentration of Tb³⁺.（4）The bandgap ofβ-Ga₂O₃:Gd³⁺decreased at low Gd³⁺concentration,and then increased with the increase of Gd³⁺doped amount.2.The experiment research on Tb³⁺-doped gallium oxide.Ga₂O₃:Tb³⁺was synthesized by hydrothermal and calcination processes,and influence of the initial p H of solutions,reaction time,annealing temperature and time on properties of the material was investigated.The results are as follows:（1）All unannealed samples were Ga OOH:Tb³⁺.And the photoluminescence effect of unannealed samples prepared in solutions with p H=8 or 10 was the best.（2）The samples with hydrothermal reaction time at 12h or 24h showed the highest relative emission intensity.（3）Ga OOH:Tb³⁺transforms into a mixture ofα-Ga₂O₃:Tb³⁺andβ-Ga2O3:Tb³⁺.And the optimal annealing temperature was 800℃.（4）As the annealing time increased,the PL intensity of Tb³⁺decreased slightly.3.The experiment research on Tb³⁺-doped(Gd_xGa_1-x)₂O₃.(Gd_xGa_1-x)₂O₃:Tb³⁺（x=0,0.1,0.3,0.5,07）was synthesized by hydrothermal and calcination processes,and influence of annealing temperature,annealing time,and Gd³⁺content on properties of the material was investigated.The results are as follows:（1）With annealing temperature increasing,the crystallization quality of（Gdx Ga1-x）2O3（x=0.5）was improved,and its luminous performance was improved obviously.（2）With annealing time increasing,the morphology of（Gdx Ga1-x）2O3（x=0.5）had no obvious change,but its luminescence intensity was improved slightly.（3）(Gd_xGa_1-x)₂O₃:Tb³⁺with different Gd³⁺contents showed different structures and luminous characteristics.With optimal quality and high purity,（Gdx Ga1-x）2O3:Tb³⁺（x=0.3）possesses favorable photoluminescence properties when excited by light with suitable wavelength.