Heat treatments of Tanzania ruby as monitored by ESR spectroscopy

Abstract

The main purpose of heat treatment is to find the optimum condition to either enchance or reduce the color in order to increase value of ruby. It was found that by heating a slightly bluish Tanzania ruby in oxygen gas atmosphere could lead to a more perfect ruby. While X-ray diffractometer found the maximum decrease in c/a ratio of the hexagonal structure after the heat treatment at 1200°C, the number of Fe2+ions converted to Fe3+was detected by electron spin resonance spectrometer and found to increase with heating temperatures. These were clearly two factors that reduced blue color in the Tanzania ruby. The best heat treating temperature to enhance the quality of the ruby was at 1300°C.