Effect of environment upon the melting point of Al2O3
- 1 July 1967
- journal article
- Published by National Institute of Standards and Technology (NIST) in Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
- Vol. 71A (4) , 317-333
- https://doi.org/10.6028/jres.071a.038
Abstract
The melting point of Al2O3 has been determined in vacuum, air, argon, and helium utilizing iridium or tungsten containers. All melting point experiments were conducted in induction furnaces capable of heating small samples under blackbody conditions to 3000 °C in vacuum. 2600 °C in inert atmospheres, and 2400 °C in air. Temperatures were continuously monitored with a recording photoelectric pyrometer which has a sensitivity of ±0.2° at 1063 °C and ±1° at 2000 °C. Melting points were determined on specimens having a purity in excess of 99.9 percent. The data indicated that the melting point of Al2O3 determined in vacuum (~ 6.5 × l0-5 torr) is 2051 °C (1FTS). The overall maximum uncertainty was estimated to be ±6 °C. The measurements themselves were precise within ±1.5 °C. Vacuum treatment had least detrimental effect upon the Al2O3 specimens. Each of the gaseous atmospheres including air yielded lower melting points for Al2O3, presumably due to a premelting phenomenon.Keywords
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