Discovery And Photoluminescence Of Red/orange-emitting La_26-xSr_xSi₄₁O_x+1N_80-x:Eu²⁺/Ce³⁺（x=12.72-12.90） Novel Phosphors For High Color Rendition White LEDs

Rare-earth-activated phosphors are playing key roles in controlling the optical quality of phosphor-converted white light-emitting diodes（pc-wLEDs）,but it is still a challenge to discover new phosphors with interesting properties or structure.In this work,we applied the single-particle-diagnosis approach to screen and find phosphors in the multi-nary system La-Sr-Si-O-N,and discovered broadband red-or orange-emitting La_26-xSr_xSi₄₁O_x+1N80-x:Eu²⁺/Ce³⁺（x=12.72-12.90）phosphors.The single-crystal structure refinement results show that La_13.1Sr_12.9Si₄₁O_13.9N_67.1（x=12.9）crystallizes in the hexagonal system（space group P6,No.174,Z=3）with a=b=17.3506（5）?,c=22.4052（6）A.The crystal structure of La_26-xSr_xSi₄₁O_x+1N80-x consists of three-dimensional frameworks formed by edge-,corner-and face-sharing Si（O,N）4 tetrahedra,where 23 independent and disordered La/Sr atoms are embedded in one unit cell.We synthesized pure phases doped with Eu²⁺/Ce³⁺ and confirm the phase purity by various characterization methods.Under 450 nm excitation,the Eu²⁺-doped sample shows broad band red emission(λ_em=643 nm,full-width at half maximum（FWHM）=3477 cm-1（140 nm）),and the Ce³⁺-doped one gives an orange emission(λ_em=568 nm,FWHM=4700 cm-1（155 nm）).We prepared white LEDs by combining two newly discovered phosphors with blue LED(λ_em=450 nm)and commercial green phosphor(Y3（Al,Ga）5O12:Ce³⁺,λ_em=520 nm).Its color coordinate was x=0.3492,y=0.348,color rendering index Ra was 84.2,and color temperature（CCT）was 4831 K.Due to the low quantum efficiency of phosphors,the luminous efficiency of this wLED was only 9.46 lm/W K,which still needs to be improved.This study not only developed a new type of nitride luminescent materials,but also provided a case for understanding the internal relationship between structure and properties in luminescent materials.The main research results of this study are summarized as follows:1.We discovered a new type of phosphor matrix material La_13.1Sr_12.9Si₄₁O_13.9 N_67.1 in La-Sr-Si-O-N multivariate system by single-particle-diagnosis approach,and parsed its crystal structure.2.We synthesized nearly pure Eu²⁺or Ce³⁺doped La_26-xSr_xSi₄₁O_x+1N80-x（x=12.72-12.90）phosphors by high temperature and pressure sintering technology.Under the excitation of blue light,the phosphors exhibited broad band red（～643 nm）or orange（～583 nm）emission,respectively.And their applications in white LEDs are verified.3.We clarify the structure-activity relationship between crystal structure and luminescent properties of the luminescent materials,which provides a reference for further exploration and development of new luminescent materials.