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 Pnnm (no. 58) with a = 9.5923(2), b = 21.3991(5), c = 5.8889 (2) Å and Z = 2, while BaSi4Al3N9:Eu2+ in the space group of P21/C (no.14) with a = 5.8465(4), b = 26.7255(18), c = 5.8386(4) Å, β =
118.897° and Z = 4. The single-particle photoluminescence
of Ba5Si11Al7N25:Eu2+ shows yellow emission (λem = 568 nm, fwhm
= 98 nm) and a quantum efficiency of 36% under the 405 nm excitation.
BaSi4Al3N9:Eu2+ shows
blue emission (λem = 500 nm, fwhm = 67 nm) upon the
365 nm excitation.