XPS and ToF-SIMS analysis of natural rubies and sapphires heated in an inert (N 2 ) atmosphere

Microscopic origin of the optical processes in blue sapphire

“…Recent studies by Achiwawanich et al (2007) report that when heated in an inert atmosphere, the intensity of the dark blue colour of sapphire increases up to approximately 1500 K. 19 This evidence seems to support our conclusion that IVCT is responsible for the colour of sapphire. The increased mobility of ions in the structure increases the probability of Fe-Ti pairs forming and hence charge transfer occurring.…”

The Annealing of Corundum (Ruby) in Nitrogen (N2) Air

“…Depending on the impurity ratio, the ruby color may vary [3,4]. On the other hand, when Al +3 ions are replaced by Fe +3 , Fe +2 and Ti +4 ions, blue corundum (sapphire) is formed [5]. Color is important in the quality of rubies.…”

“…Heat treatments of sapphire and ruby have been studied extensively. However, many are hidden because they are commercial [5]. For this reason, a unique heat treatment is required for the development of the quality of the rubies in each country.…”

“…[6,7]. In addition, when the Myanmar rubies are annealed in an inert atmosphere at 1000-1200°C, the blue color of the ruby is slightly dispersed [3,5,8]. The stains that affect the quality of Ruby can be removed by annealing in an oxidative or reductive environment.…”

Characterization of dark core and blue patch in Mong Hsu ruby

“…Later many researchers have been interested in rubies from Mong Hsu because of their typical characteristics such as separated color zoning with dark cores, blue patch and transparent red rims. The dark core and blue patch can be easily eliminated by the heat treatment under reducing or oxidizing atmosphere [4,5]. Peretti et al reported the characteristics of the violet core and red rim in untreated ruby by the UV-VIS-NIR spectroscopic analysis, showing the difference in the intensities of absorption band in range of 550~800 nm, without mentioning on the blue patch characteristic [6].…”