Preparation And Properties Of Ce³⁺ Doped Alkali Earth Metal Rare Earth Oxide Phosphors

White light emitting diodes?WLEDs?,as the latest solid-state lighting source,have gradually replacing other traditional lighting sources due to the advantageous characteristics in energy saving,environmental protection and long service lifetime.Phosphor is an important part of WLEDs,which is mainly composed of rare earth ions(Ce³⁺,Eu²⁺)doped materials.Alkaline earth metal rare earth oxide is an important Ce³⁺doped phosphor host,which mainly includes A₃B₄O₉ and AB₂O₄ structure.The six-coordination environment of Ce³⁺in A₃B₄O₉:Ce³⁺is conducive to red light emission,and the eight-coordination of Ce³⁺in AB₂O₄:Ce³⁺is conducive to green light emission.In order to supplement the research blank of oxide red photoluminescence,Ce³⁺ions are introduced into Ba₃Lu₄O₉ host,and Ba₃Lu₄O₉:Ce³⁺orange-red phosphors are successfully prepared and characterized in detail.In addition,in order to simplify the packaging process of WLED,the Sr₃Sc₄O₉:Ce³⁺red phosphor is realized by using the ion exchange method,and the color tuning from red to green.The prepared Ce³⁺ions doped Sr₃Sc₄O₉-CaSc₂O₄ phosphors can be directly matched with the blue chip for white light output.Replaced part of Ca²⁺and Sc³⁺ions by Y³⁺and Mg²⁺ions in CaSc₂O₄:Ce³⁺,the emission of prepared sample?CSO-YMg?red-shifted from green to yellow,which could directly match with the blue chip for white light output.The main experimental conclusions are as follows.The novel Ba₃Lu₄O₉:Ce³⁺orange-red phosphors are successfully synthesized by the high-temperature solid-state reaction and the preparation process was optimized according to the optical properties.The optimal preparation condition is the single-pass sintering in H₂ and the optimal Ce³⁺-doped concentration is 0.5 at.%.The strongest excitation and emission peaks of Ba₃Lu₄O₉:Ce³⁺are located at 410 nm and 584 nm,respectively.Compared to reported Ba₃Sc₄O₉:Ce³⁺phosphors,the emission peak of Ba₃Lu₄O₉:Ce³⁺phosphor is effectively red-shifted about 21 nm,indicating that the increase of radius of B³⁺sites would make the emission of Ce³⁺ions shift to long-wavelengths.However,Ba₃Lu₄O₉:Ce³⁺phosphor has a strong thermal quenching,mainly due to the lattice expansion and phonon vibration.In addition,the temperature dependent emission spectrum excited by 355 nm suggesting the observed luminescence mainly comes from the Ce³⁺ions located in the Lu O₆ and BaO₆polyhedra.Besides,the WLED device fabricated with as-prepared sample,commercial green phosphors and a blue LED has a great performance with the color rendering index?Ra?exceed 90,which shows that the Ba₃Lu₄O₉:Ce³⁺phosphor has certain commercial potential.The Sr₃Sc₄O₉:Ce³⁺red phosphor was adjusted by ion exchange method to make the emission wavelength red-shift.Replaced the Sr²⁺ion by Ca²⁺ion in CaCl₂ melt,the Ce³⁺ions doped Sr₃Sc₄O₉-CaSc₂O₄ phosphor was prepared,and the preparation conditions were optimized.The optimized reaction temperature was 1173 K and the Ce³⁺ions doping concentration of Sr₃Sc₄O₉:Ce³⁺is 0.15 at.%.By controlling the proportion of CaCl₂(r_mr),the main emission wavelength of the prepared phosphor can be gradually blue-shifted from 592nm to 512 nm,the color tuning of as-prepared phosphors could be easily adjusted from red to green.In addition,combining the prepared sample(r_mr=0.1)and the blue chip,a WLED device with high color rendering?CCT=3555 K,Ra=88,R9=94?is obtained.It shows that the ion exchange method and the prepared Ce³⁺ion doped Sr₃Sc₄O₉-CaSc₂O₄ phosphor have application potential in the white light field.For CaSc₂O₄:Ce³⁺green phosphor,using Y³⁺and Mg²⁺ions replace part of Ca²⁺and Sc³⁺ions in the host,a series of samples?CSO-YMg?with different substitution ratio were prepared by high-temperature solid-state method.The obtained results indicate that in the preparation process,the Y³⁺ions can occupy both Sc³⁺and Ca²⁺sites simultaneously,resulting in the appearance of MgO impure phase.The MgO can be effectively washed through pickling.With the increase of Y³⁺and Mg²⁺ions,the main emission peak of as-prepared sample is red-shifted from 512 nm to 530 nm,the color tuning could be easily adjusted from green to yellow.As the Y³⁺ions enter into the Sc³⁺ion lattice,cerium ions(Ce³⁺,Ce⁴⁺)also enter into the Sc³⁺ion lattice,and the energy transfer between different lattice result in the such evident quenching phenomenon.Besides,utilizing the as-prepared CSO-5 phosphors and a blue chip,a cold white light WLED?CCT=6482 K,Ra=81.5?obtained with a comparable performance to those with commercial Y₃Al₅O₁₂:Ce³⁺commercial phosphors?Ra<75?,indicating that the as-prepared sample has commercial potential.