Luminescent Mechanism And Upconversion Emissions Study Of Ho³⁺,Yb³⁺ Codoped12CaO·7Al₂O₃Powders

Number of upconversion material research is increasing in recent years.Upconversion material is doped with rare earth elements in solid compounds. Themetastable energy level properties of the rare earth elements is propitious to absorbmultiple low-energy of long-wave, which allows the infrared light into visible lightafter multi-photon plus and emit short-wave radiation. Hence, upconversion materialscan use in infrared light display, anti-counterfeit, illumination, laser and biologicaltracer.The type of upconversion materials is mainly fluoride, oxyfluoride or sulfide andso on. This thesis is based on oxide C12A7matrix material. It is not only beneficial toHo³⁺ion upconversion luminescence,but also conducive to Yb³⁺ion sensitize Ho³⁺ion.This owes to C12A7material band gap of5.9eV, and its special nanocage structure,and O2-embedded in the cage cause distortion and its symmetry to lower.The different Yb³⁺concentration of the Ho³⁺,Yb³⁺doped C12A7upconversionpowders are prepared by chemical precipitation method and excited by980nm laser.The emissions from Ho³⁺ions are observed at396nm,429nm,549nm,662nm and760nm assigning to⁵G₄â†'⁵I₈，⁵G₅â†'⁵I₈，⁵F₄（⁵S₂）â†'⁵I₈,⁵F₅â†'⁵I₈，⁵F₄（⁵S₂）â†'⁵I₇.According to the upconversion emissions intensity of green and red in the differentYb³⁺concentrations of upconversion powder samples, Ho³⁺ion green emissionintensity is significantly enhanced by Yb³⁺concentration increased. Owing to theupconversion emissions intensity of green and red in the powder samples and laserpower change non-liner, the avalanche-like phenomenon of0.1%Ho³⁺, x%Yb³⁺doped C12A7powder samples is observed. After vacuum heat treatment, theupconversion luminescence intensity of Ho³⁺is enhanced due to the C12A7specialnanocage structure and its symmetry to lower.