X-ray absorption spectroscopy of sapphires from different geological provenances

Name: Natthapong Monarumit

LCSH: Kasetsart University -- Dissertations. Ph.D. (Earth Science and Technology) 2017

Classification :.LCCS: QE394.S3

LCSH: Kasetsart University. Department of Earth Sciences -- Dissertations

LCSH: Sapphires -- Spectra

LCSH: X-ray spectroscopy

Abstract: Sapphire is a variety of gem corundum consisting of Al2O3 and trace elements to produce its color. Natural sapphires have originated from different geological provenances relating to basaltic host rock and metamorphic one. In this study, X-ray Absorption Spectroscopy (XAS) focused on X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) is applied for analyzing the crystal structure of sapphires including the oxidation states of Fe and Ti as well as the Fe-O and Ti-O bond lengths. XAS is cooperated with other techniques such as ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and electron probe micro analysis (EPMA). The blue color of blue sapphires with various conditions showed absorption bands at 710 nm and 580 nm detected from UV-Vis-NIR spectra. The Fe and Ti content of sapphire samples from both basaltic and metamorphic origins were detected by LA-ICP-MS to find the suitable sample for XAS analysis. The different micro-inclusions between high-quality sapphires and natural sapphires were investigated by EPMA. The ilmenite micro-inclusion was present in natural sapphires from both geological origins but it was absent in high-quality sapphires. As a result, the oxidation states of Fe and Ti in sapphire host structure were Fe3+ and Ti4+ using Fe K-edge and Ti K-edge XANES spectra confirmed with Fe-O and Ti-O bond lengths from EXAFS spectra. The blue color of blue sapphires was originated from Fe3+/Ti4+ mixed acceptor states. However, the Fe2+ oxidation state derived from ilmenite micro-inclusion was detected in natural sapphires.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Somruedee Satikune

Role: Thesis Advisor

Name: Wiwat Wongkokua

Role: Thesis Co-Advisor

Created: 2017

Modified: 2023-06-21

Issued: 2023-06-21

วิทยานิพนธ์/Thesis

application/pdf

URL: https://kasetsart.idm.oclc.org/login?url=https://www.lib.ku.ac.th/KUthesis/2560/natthapong-mon-all.pdf

CallNumber: QE394.S3.N38

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Earth Science and Technology

Grantor: Kasetsart University

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