Esijolomi Benjamin Otokunefor; Samuel Ogochukwu Azi
Abstract
Optical float zone furnaces are used in crystal growth experiments where contact temperature measuring devices are not used, in order to avoid contamination. However, they are factory ...
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Optical float zone furnaces are used in crystal growth experiments where contact temperature measuring devices are not used, in order to avoid contamination. However, they are factory calibrated in terms of the applied lamp power and when in use, melting points are carefully controlled by visual monitoring using video cameras. There is therefore, the need to devise a means to recalibrate the percentage lamp power settings as temperatures (o C) for any sample being processed. To achieve this, a float zone furnace using ellipsoidal flood light reflectors has been designed, constructed and thermally characterized. The design specification was tailored around two ellipsoidal, commercial flood lighting aluminum reflectors of semi major axis a = 31.0 cm, semi minor axis, b = c = 25.5 cm and eccentricity e = 0.587 and powered by 2000W, rectangular halogen filament. The temperature distributions at and around the secondary focus of the realized furnace was calibrated against lamp voltage and power using a K-type thermocouple connected to a TES 1315 temperature data logger. The temperature growth of heated samples with applied lamp power was found to be described by an inverse exponential expression with a goodness of fit value of 99.48% after least square regression and is statistically significant. Using the determined temperature-power relationship, it is thus possible to determine the temperature of heated samples without a thermometer. Secondly, optical float zone furnaces can be temperature calibrated against input power.
