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Spray drying makes better YAG

21 Oct 2005

A low-temperature process for synthesizing YAG could benefit manufacturers of solid-state lasers.

Researchers in Mexico have developed an efficient way of synthesizing yttrium aluminium garnet (YAG) - an important raw material in solid-state laser crystals. The low temperature, spray drying process not only saves energy, but also gives material with good processing characteristics. (AZojomo - Journal of Materials Online, DOI: 10.2240)

Consisting of spherical particle agglomerates 2 µm in diameter, the YAG precursor powder is formed at temperatures of less than 900 degC. The use of as low a temperature and as a short processing time as possible is desirable to restrict grain growth and enhance the material's mechanical properties.

Scientists from Universidad Michoacana de San Nicolás de Hidalgo, fed a solution of aluminium nitrate, yttrium nitrate, ethylene glycol and citric acid into a spray dryer to evaporate the solvent and transform the mixture into a homogeneous wet powder. The team then treated samples of the powder at a range of temperatures from 750 to 1200 degC for a period of 1 hour.

Using thermal analysis and XRD measurements, the group discovered that a calcination temperature of just 825 degC was sufficient for a pure YAG phase to form.

"The employment of spray drying diminishes the processing time with regard to other methods and maintains the high degree of components mixing, moreover it has an important energy saving," say the authors in their paper. "The most important parameters in the YAG formation are the enhanced distribution of aluminium and yttrium ions and the shortening of the effective diffusion distances."

James Tyrrell is reporter on Optics.org and Opto & Laser Europe magazine.

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