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Luminescent ceramics for LED applications

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The LED lighting market is growing of about 30 % per year because of various concurrent factors. Traditional incandescent lighting will soon be prohibited in Europe and USA whereas it is already in Australia and numerous requests come from the governments for low energy consumption components. LED systems are currently proposed for:

  • External lighting,
  • Commercial lighting,         
  • Retrofit and solar energy systems.

For a widespread diffusion (as for example for domestic and high power lighting) few problems must be solved. A critical feature is the material used as light converter. It is formed by a silicone matrix where particles of the converting material are embebbed (generally Ce:YAG). The silicone matrices suffer a low transmittance because of the high light scattering, thus affecting the quality and quantity of the emitted light.

At ISTEC polycrystalline Ce:YAG materials are currently under investigation to replace the silicone matrices. The advantages of the ceramic phosphors compared to the silicone based matrices are numerous:

  • Better light quality (closer to natural light),
  • Higher thermal stability,
  • Higher efficiency,
  • Constant performances over time,

New possibilities for the domestic lighting market, that is not served by the current commercial LEDs.

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PROCESSES & FACILITIES:

The phosphor ceramics studied at ISTEC as light converters for LEDs are formed by polycrystalline YAG generally doped with Ce (1-3 at %).

The production process starts with the mixing of the selected powders, that must be highly pure, micrometric or nanometric and with a regular and controlled morphology. Shaping is by pressing and sintering is under controlled, highly pure atmosphere.

Compositional graded or layered structures and various geometries are possible with this processing technique.

PRINCIPALI COLLABORAZIONI SCIENTIFICHE:

  • Joanneum Research Institute, Austria
  • Tridonic Jennersdorf GmbH, Austria
  • Imperial College, Londra, Gran Bretagna