Physicists from Yekaterinburg have generated yttrium-aluminum-garnet nanopowder using the laser-induced evaporation method. The powder with particles sized about 10 nanometers was used to create optic ceramics with a high infrared light transmission factor.

The laser-induced evaporation method also known as laser ablation or laser spark is based on removing a substance from the surface during laser irradiation. The method works in several stages: the material evaporation from the target; plasma torch development from the particles of the substance being irradiated; deposition and growth of the crystal material on the substrate. The process can be used for chemical analysis of substances as well as for technologies associated with surface processing and nanostructure generation.

The task of creating nanopowders with predetermined stoichiometry — that is, pre-determined ratio of the masses of chemical elements included in the powder — is a promising one. The main challenge of the technology is associated with excessive substance evaporation; therefore laser irradiation with optimum parameters is required. The laser used to produce the powder must be high-power and with a short radiation pulse at the same time. Experts at the Institute of Electrophysics, Ural Branch of Russian Academy of Sciences, suggested using carbon-dioxide laser for the purpose (the active environment of such laser is a gaseous mixture with a high level of CO₂ content). The physicists describe the advantages of such laser for generating nanopowders with predetermined stoichiometry in a report that is to be published in the January issue of the Letters to the Technical Physics Journal that is already made available at the journal Web site.

Physicists Vladimir Osipov, Vasily Lisenkov and Vyacheslav Platonov developed a theoretical model of the laser beam interaction with the substance, and subsequently confirmed the model experimentally. In order to obtain nanopowder, a laser complex consisting of a pulse-periodic CO₂ laser, evaporative chamber, and a separation and nanopowder capturing system was used. The laser received impulses with peak capacity of up to 10 kilowatt and repetition frequency of 500H. Yttrium and aluminium oxides served as impulse targets, with the particles sized from one to ten micron. As a result of ablation, the researchers generated an amorphous yttrium-aluminium oxide powder (also called yttrium aluminum garnet as synthetic precious stone is made from the substance on the microlevel). The size of the particle was 10 nanometer. The speed of the powder production depends on the radiant energy. The use of the CO₂ laser allowed to generate 24 grams of the powder per hour.

In order to show the practical importance of the resultant nanopowder, the researchers used it to make several samples of transparent optical ceramics. Such ceramics lets through 77 per cent of infrared radiation which makes it a promising material for electronics to manufacture infrared windows (areas transparent for infrared irradiation).

Source of information: “The Laser Synthesis of Nanopowders in the Yttrium Aluminum Garnet Stoichiometry,” V. V. Osipov, V. V. Lisenkov, V. V. Platonov, the Letters to the Technical Physics Journal, 2011, vol. 37, issue 1, pp. 103-110

Further information: Vasily Lisenkov, Ph. D. (Physics and Mathematics), the Quantum Electronics laboratory. Telephone: +7 (343) 267-87-79, e-mail: lisenkov@iep.uran.ru