Full text

Turn on search term navigation

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

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.

Details

Title
The Covariation of Color and Orange Fluorescence Instabilities in Yellow Sapphires
Author
Yang, Yunqi 1 ; Wang, Chaowen 2   VIAFID ORCID Logo  ; Wang, Chengsi 1 ; Shen, Xibing 3 ; Yin, Ke 4 ; Chen, Tao 1 ; Shen, Andy Hsitien 1   VIAFID ORCID Logo  ; Algeo, Thomas J 5   VIAFID ORCID Logo  ; Hong, Hanlie 6 

 Gemmological Institute, China University of Geosciences, Wuhan 430074, China; [email protected] (Y.Y.); [email protected] (C.W.); [email protected] (T.C.); [email protected] (A.H.S.); Hubei Gems and Jewelry Engineering Technology Research Center, Wuhan 430074, China 
 Gemmological Institute, China University of Geosciences, Wuhan 430074, China; [email protected] (Y.Y.); [email protected] (C.W.); [email protected] (T.C.); [email protected] (A.H.S.); Hubei Gems and Jewelry Engineering Technology Research Center, Wuhan 430074, China; Department of Geosciences and Engineering, Delft University of Technology, 2628 CN Delft, The Netherlands 
 School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; [email protected] (X.S.); [email protected] (K.Y.); [email protected] (H.H.); School of Resources and Environment, Beibu Gulf University, Qinzhou 535011, China 
 School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; [email protected] (X.S.); [email protected] (K.Y.); [email protected] (H.H.) 
 Department of Geosciences, University of Cincinnati, Cincinnati, OH 45221-0013, USA; [email protected]; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China; State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China 
 School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; [email protected] (X.S.); [email protected] (K.Y.); [email protected] (H.H.); State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China 
First page
663
Publication year
2023
Publication date
2023
Publisher
MDPI AG
e-ISSN
2075163X
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2819477653
Copyright
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.