Abstract
Scandium is being explored as an alloying element for aluminium alloys, which are gaining importance as high-performance lightweight structural alloys in the transportation industry. Sc-rich ScAlN thin films show strong piezoelectricity and can be fabricated on a hard substrate for use as wideband surface acoustic wave filters in next-generation wireless mobile communication systems. However, the use of ScAlN thin films in microelectromechanical system devices is limited by the high cost of metallic Sc, which is due to the difficulty in smelting of this material. Here, we propose a novel microwave irradiation process for producing Al-Sc alloys, with Mg ions as a reducing agent. Although scandium oxide is thermodynamically stable, intermetallic Al3Sc is obtained in high yield (69.8%) via a low-temperature (660 °C) reduction reaction under microwave irradiation. Optical spectroscopy results and thermodynamic considerations suggest a non-thermal equilibrium reaction with the univalent magnesium ions excited by microwave irradiation.
Highlights
Scandium is the 31st most abundant element in the earth’s crust, with a Clarke number of 22 ppm[1]
Hashimoto et al reported that a surface acoustic wave (SAW) resonator based on the ScAlN/6H-SiC structure exhibited resonance Qr, antiresonance Qa, and K2 values of 340, 240, and 4.5%, respectively, at 3.8 GHz
The raw material for this process, is thermodynamically stable. It is converted into scandium fluoride, which is reduced at 1873 K using metallic calcium as the reducing agent, according to the following reactions[14]: Sc2O3 + 6HF −> 2ScF3 + 3H2O
Summary
Scandium is the 31st most abundant element in the earth’s crust, with a Clarke number of 22 ppm[1].
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