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ThermoRaman spectroscopic study of kintoreite
Ray L Frost1, Matt L Weier, Wayde Martens
1Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, G.P.O. Box 2434, Brisbane, Qld. 4001, Australia. r.frost@qut.edu.au
Summary
ThermoRaman spectroscopy revealed the molecular structure and thermal decomposition of kintoreite, a phosphate mineral. This study characterized its dehydration and dehydroxylation processes using spectroscopy.
Area of Science:
- Mineralogy
- Spectroscopy
- Materials Science
Background:
- Kintoreite (PbFe3(PO4)2(OH,H2O)6) is a phosphate mineral belonging to the jarosite group.
- Infrared spectroscopy indicated significant water and hydroxyl content in kintoreite.
- Infrared spectroscopy revealed no water in segnitite, the arsenojarosite analogue.
Purpose of the Study:
- To investigate the molecular structure of kintoreite using Raman and ThermoRaman spectroscopy.
- To determine the thermal decomposition behavior, including dehydration and dehydroxylation, of kintoreite.
- To compare the structural and compositional features of kintoreite with segnitite.
Main Methods:
- ThermoRaman spectroscopy was employed to study molecular structure and thermal decomposition.
- Infrared spectroscopy was used to identify water and hydroxyl groups.
- Raman spectroscopy at 77 K was utilized to analyze vibrational modes.
Main Results:
- Raman spectra at 77 K showed characteristic bands for phosphate (PO4)3-, sulfate (SO4)3-, and arsenate (AsO4)3- units.
- Specific bands at 974.6, 1003.2, and 866.5 cm(-1) were attributed to symmetric stretching vibrations.
- Bands at 583.7 and 558.1 cm(-1) were assigned to (PO4)3- bending modes.
- ThermoRaman spectroscopy identified temperature ranges for dehydration and dehydroxylation in kintoreite.
Conclusions:
- Raman spectroscopy confirmed the presence of both arsenate and phosphate in the kintoreite structure.
- The study successfully characterized the thermal decomposition processes of kintoreite.
- Spectroscopic methods provided insights into the molecular structure and water content of kintoreite and segnitite.