Transparent polycrystalline YAG doped with neodymium: synthesis parameters, laser efficiency

Neodymium doped YAG (Y₃Al₅O₁₂, yttrium aluminium garnet) is one of the best known single crystal laser materials. A new method for the synthesis of neodymium doped YAG in transparent polycrystalline form is developed. Two preparation techniques have been considered for the production of ceramics. The first method is a "chimie douce" route in order to obtain nanoparticles with a very homogeneous mixture of the constituents. The starting powder results from the decomposition of an organo-metallic solution. Aluminium, yttrium and neodymium nitrates are dissolved with citric acid in water. After the evaporation of the solvent, and the heating of the resulting "cake" in air between 700 °C and 1100 °C, nanoparticles are obtained. The second synthesis technique, commercial oxide powders are utilized as precursors: Al₂O>₃, Y₂O₃, Nd₂O₃, and SiO₂ added as a sintering aid. After mixing, these powders are compacted in an isostatic or uniaxial press between 50 MPa and 800 MPa. The green compact is then introduced into a vacuum furnace and sintered at high temperature. In this work, the most important parameters (pressure, composition, sintering temperature) have been studied and optimized in order to enhance the transparency of the ceramics and improve laser efficiency.