Yunqi Yang
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Yunqi Yang has a total of 8 co-authors. Here are the top co-authors by number of shared publications:
- Andy Hsitien Shen
Gemmological Institute, China University of Geosciences (Wuhan), Wuhan 430074, China
1 shared publication - Chaowen Wang
Gemmological Institute, China University of Geosciences, Wuhan 430074, China
1 shared publication - Chengsi Wang
Gemmological Institute, China University of Geosciences, Wuhan 430074, China
1 shared publication - Hanlie Hong
School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
1 shared publication - Ke Yin
School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
1 shared publication - Tao Chen
Gemmological Institute, China University of Geosciences, Wuhan 430074, China
1 shared publication
Latest Publications
- Open Access
The Covariation of Color and Orange Fluorescence Instabilities in Yellow Sapphires
In recent years, some sapphires were found to fade in sunlight and to increase their color after UV irradiation. This unstable color phenomenon is attributed to the photochromism of corundum. The photochromic effect seriously affects the grading and evaluation of sapphires, although its mechanism is still uncertain. Here, we performed a set of photochromic experiments on sapphire specimens using a 254 nm shortwave UV light source and a D65 light source (which simulates sunlight) to generate different color states exhibiting characteristic absorption, emission, and excitation spectra. We observed that, for different color states, variation in the intensity of the absorption band at ~460 nm was consistent with that of orange fluorescence at 500–800 nm. This observation indicates a relationship between color instability and orange fluorescence. Peaks in excitation spectra at 320, 420, 490, 560, and 637 nm provide insight into the source(s) of excited orange fluorescence, which are related to different types of F-centers and Mg-trapped holes. We propose an explanation for the photochromic phenomenon: the color of photochromic yellow sapphire is the result of a variety of defects that release orange fluorescence simultaneously. Further, we hypothesize that the mechanism of photochromism in yellow sapphires is linked to electron transfer between F-centers and Mg-trapped holes.
Open AccessThe Covariation of Color and Orange Fluorescence Instabilities in Yellow Sapphires
In recent years, some sapphires were found to fade in sunlight and to increase their color after UV irradiation. This unstable color phenomenon is attributed to the photochromism of corundum. The photochromic effect seriously affects the grading and evaluation of sapphires, although its mechanism is still uncertain. Here, we performed a set of photochromic experiments on sapphire specimens using a 254 nm shortwave UV light source and a D65 light source (which simulates sunlight) to generate different color states exhibiting characteristic absorption, emission, and excitation spectra. We observed that, for different color states, variation in the intensity of the absorption band at ~460 nm was consistent with that of orange fluorescence at 500–800 nm. This observation indicates a relationship between color instability and orange fluorescence. Peaks in excitation spectra at 320, 420, 490, 560, and 637 nm provide insight into the source(s) of excited orange fluorescence, which are related to different types of F-centers and Mg-trapped holes. We propose an explanation for the photochromic phenomenon: the color of photochromic yellow sapphire is the result of a variety of defects that release orange fluorescence simultaneously. Further, we hypothesize that the mechanism of photochromism in yellow sapphires is linked to electron transfer between F-centers and Mg-trapped holes.