Yttrium aluminium garnet
Yttrium -aluminum-garnet ( YAG short ) is a crystalline compound artificially produced with the chemical composition Y3Al5O12. A similar in structure, also artificial crystal yttrium iron garnet ( YIG yttrium iron garnet for English ).
YAG has very high acoustic wave velocities, which differ in their different spatial directions only slightly. The longitudinal wave velocity in direction 8563 m / s and for the transverse wave velocity in the direction of 5029.3 m / s The Isotropiefaktor is 1.03.
The production of YAG is almost exclusively by the Czochralski method (CZ method ), can be bred using the single crystals of more than 300 mm in length and up to 100 mm diameter.
Laser and LED
YAG is mainly used as a single-crystal host crystal for solid-state lasers. For this purpose it is, depending on the desired properties, especially the wavelength to be emitted doped with various lanthanide, including neodymium (Nd: YAG laser) and erbium (Er: YAG ) laser.
For the production of white LEDs can be doped with cerium powder YAG (YAG: Ce 3 ) can be used as a yellow phosphor in combination with a blue LED ( indium gallium nitride InGaN ). YAG: Ce3 single crystals are still as scintillators in scanning electron microscopes (SEM ) is used, where they are used to generate particularly low-noise images.
YAG ( gemmologically correct: Granatoid ), with its Mohs hardness of 8 to 8.5, and its high dispersion and refractive index ( together they form the so-called fire) also a popular gemstone. Colorless and under the trade names simulated diamond, Diamonair or Cirolit he served as a diamond substitute, until it was replaced by the more appropriate Zirconia. Depending on doping with different elements and thus offers a green, yellow, blue, red and violet can also be used to imitate other gemstones.