The Preparation And Properties Of Al₂O₃-based Phosphor Ceramic For Application In Laser-driven Lighting

As a new illumination,laser-driven lighting has potential applications in high power illuminators for its good collimation,small size,and long distance.The phosphor materials is a key component in the laser-driven lighting,where the blue laser can be converted to yellow light by the phosphor materials.The performance of laser-driven lighting is determined by the properties of the phosphor materials.Due to the high flux of laser,the temperature of the phosphor materials is high.The high temperature may lead to the degradation of illuminate properties,which suggests that super-high solid-state lighting cannot be obtained.Compare to other phosphor in laser-driven lighting,the Al₂O₃-based ceramic has an advantage in thermal conductivity,thermal stability,and low sinter temperature.At present,more and more attention has been paid to the research of fluorescent ceramics for laser illumination.The luminous saturation and the color rendering index?CRI?of the ceramic are still need to be investigated.In this paper,Al₂O₃-based fluorescent ceramics were prepared by SPS.It could be used to study the relationship between the microstructure and the saturated input power densitty by three aspects:component content,light transmission path and quantum efficiency.In order to improve the CRI of fluorescent ceramics,YAG:Mg/Mn powder was prepared.The CRI of phosphor ceramics was optimized by designing two kinds of Al₂O₃-based fluorescent ceramics.?1?The preparation and properties of Al₂O₃/YAG:Ce fluorescent ceramics.In laser-driven lighting,the saturated input power density of fluorescent materials depends on the heat.Firstly,the effects of YAG:Ce content on the microstructure,thermal properties,optical properties,and saturated input energy density were investigated.The results showed that the thermal conductivity and linear-transmittance of ceramics decrease when the YAG:Ce content increases.When the YAG:Ce content was lower than 20wt%,the saturated input energy density could be reached to 27.2W/mm².When the YAG:Ce content was above 20wt%,the saturated input energy density decreased with the increasing of YAG:Ce.The reason was that the thermal conductivity decreased.Secondly,Al₂O₃/20wt%YAG:Ce was used as the raw material and the ceramic was fabricated by SPS with different pressure and different loaded temperature in the Ar atmosphere.When the pressure increased and the loaded temperature went down,the grain size of Al₂O₃ changed,while the size and the number of pores decreased.As a result,the penetrated path of the light in the material was shorten.When the pressure was80 MPa and the loaded temperature was 1100°C,the penetrated path of the light in the ceramic was the shortest,so a higher saturated input energy density could be obtained?33.2W/mm²?.Finally,Al₂O₃/20wt%was used as the raw material.The composite ceramics with different phosphor particle sizes were prepared at 80 MPa and the loaded temperature was 1100°C.With the improvement of the phosphor particle size,the quantum efficiency changed.With the enchancement of the quantum efficiency,the saturated input energy density improved.When the quantum efficiency was 0.72 and no luminescence saturation could be found when the input energy density was 37.2W/mm².?2?The preparation of YAG:Mn/Mg red phosphor.The phosphor powder was prepared by the high-temperature solid-state method.The effect of sinter temperature and ion doping on the luminescent properties of phosphors were investigated.The results showed that the intensity of emission spectra of phosphor increased gradually when the temperature uplifted.The band gap of the matrix decreased as the ion doped concentration uplifted,which was attributed to the thermal ionization of the luminescence center.Therefore,when the doping concentration is 0.005 and the temperature is 1500°C,the pefermence of the phosphor is the highest.?3?The improvement of the CRI for the phosphor ceramics.Al₂O₃/YAG:Ce/YAG:Mn/Mg was used as raw material.The fluorescent ceramics with different structures:blending structure and the laminated structure was prepared.In laser lighting,the correlated color temperature?CCT?of ceramics decreaseed from 5077K to4866K,and the CRI increased from 54.8 to 60.8.In the laminated structure,when the laser incident surface of the ceramic was different,the performance of the material was different.Compared to Al₂O₃/YAG:Ce,the CRI of ceramics is higher?62?and the CCT is lower?5048K?when the laser irradiated the Al₂O₃/YAG:Mn/Mg layer.