Discovery of New Nitridosilicate Phosphors for Solid State Lighting by the Single-Particle-Diagnosis Approach

Discovery of novel luminescent materials is of fundamental importance in the advancement of solid state lighting and flat panel display technologies. In this work, we report a single-particle-diagnosis method for the discovery of new phosphors by just characterizing a luminescent crystalline particle as small as 10 μm in diameter. We explored single-particle fluorescence imaging and spectroscopy techniques to evaluate the photoluminescence of a phosphor particle distinguished from a complex powder mixture and applied a high-resolution single-crystal X-ray diffractometer to determine its crystal structure. The approach enabled us to discover two new phosphors in the Ba₃N₂–Si₃N₄–AlN ternary system: Ba₅Si₁₁Al₇N₂₅:Eu²⁺ and BaSi₄Al₃N₉:Eu²⁺. Ba₅Si₁₁Al₇N₂₅:Eu²⁺ crystallizes in the space group of <i>Pnnm</i> (no. 58) with <i>a</i> = 9.5923(2), <i>b</i> = 21.3991(5), <i>c</i> = 5.8889 (2) Å and <i>Z</i> = 2, while BaSi₄Al₃N₉:Eu²⁺ in the space group of <i>P</i>21/<i>C</i> (no.14) with <i>a</i> = 5.8465(4), <i>b</i> = 26.7255(18), <i>c</i> = 5.8386(4) Å, β = 118.897° and <i>Z</i> = 4. The single-particle photoluminescence of Ba₅Si₁₁Al₇N₂₅:Eu²⁺ shows yellow emission (λ_em = 568 nm, fwhm = 98 nm) and a quantum efficiency of 36% under the 405 nm excitation. BaSi₄Al₃N₉:Eu²⁺ shows blue emission (λ_em = 500 nm, fwhm = 67 nm) upon the 365 nm excitation