1 research outputs found
Stable, Heat-Conducting Phosphor Composites for High-Power Laser Lighting
Solid-state lighting using laser
diodes is an exciting new development that requires new phosphor geometries
to handle the greater light fluxes involved. The greater flux from
the source results in more conversion and therefore more conversion
loss in the phosphor, which generates self-heating, surpassing the
stability of current encapsulation strategies used for light-emitting
diodes, usually based on silicones. Here, we present a rapid method
using spark plasma sintering (SPS) for preparing ceramic phosphor
composites of the canonical yellow-emitting phosphor Ce-doped yttrium
aluminum garnet (Ce:YAG) combined with a chemically compatible and
thermally stable oxide, α-Al<sub>2</sub>O<sub>3</sub>. SPS allows
for compositional modulation, and phase fraction, microstructure,
and luminescent properties of ceramic composites with varying compositions
are studied here in detail. The relationship between density, thermal
conductivity, and temperature rise during laser-driven phosphor conversion
is elucidated, showing that only modest densities are required to
mitigate thermal quenching in phosphor composites. Additionally, the
scattering nature of the ceramic composites makes them ideal candidates
for laser-driven white lighting in reflection mode, where Lambertian
scattering of blue light offers great color uniformity, and a luminous
flux >1000 lm is generated using a single commercial laser diode
coupled to a single phosphor element