Nicola J. Horsburgh, Adrian A. Finch, Henrik Friis
{"title":"天然萤石中的镧系元素和钇取代","authors":"Nicola J. Horsburgh, Adrian A. Finch, Henrik Friis","doi":"10.1007/s00269-023-01239-4","DOIUrl":null,"url":null,"abstract":"<div><p>Fluorite is one of the most common minerals in the crust and is of widespread economic importance. It shows strong UV-excited luminescence, variously attributed to defects within the fluorite structure and lanthanide substitutions. We present here a detailed chemical characterisation of a suite of natural fluorite samples, chosen to represent the range of compositions observed in nature. We perform X-ray excited luminescence spectroscopy on the samples as a function of temperature (20–673 K) in the wavelength range 250–800 nm to provide insights into physical defects in the lattice and their interactions with lanthanide substituents in natural fluorite. Most broad bands in the UV are attributed to electronic defects in the fluorite lattice, whereas sharp emissions are attributed to intra-ion energy cascades in trivalent lanthanides. Lanthanides are accommodated in fluorite by substitution for Ca<sup>2+</sup> coupled with interstitial F<sup>−</sup>, O<sup>2−</sup> (substituting for F<sup>−</sup>) and a variety of electronic defect structures which provide local charge balance. The chondrite-normalised lanthanide profiles show that fluorite accommodates a greater proportion of heavy lanthanides (and Y) as the total Rare Earth Element (REE) concentration increases; whereas cell parameters decrease and then increase as substitution continues. Luminescence intensity also goes through a maximum and then decreases as a function of REE concentration. All three datasets are consistent with a model whereby lanthanides initially act as isolated centres, but, beyond a critical threshold (~ 1000 ppm), cluster into lanthanide-rich domains. Clustering results in shorter REE-O bond distances (favouring smaller heavier ions), a larger unit cell but more efficient energy transfer between lanthanides, thereby promoting non-radiative energy loss and a drop in the intensity of lanthanide emission.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-023-01239-4.pdf","citationCount":"1","resultStr":"{\"title\":\"Lanthanide and yttrium substitution in natural fluorite\",\"authors\":\"Nicola J. Horsburgh, Adrian A. Finch, Henrik Friis\",\"doi\":\"10.1007/s00269-023-01239-4\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Fluorite is one of the most common minerals in the crust and is of widespread economic importance. It shows strong UV-excited luminescence, variously attributed to defects within the fluorite structure and lanthanide substitutions. We present here a detailed chemical characterisation of a suite of natural fluorite samples, chosen to represent the range of compositions observed in nature. We perform X-ray excited luminescence spectroscopy on the samples as a function of temperature (20–673 K) in the wavelength range 250–800 nm to provide insights into physical defects in the lattice and their interactions with lanthanide substituents in natural fluorite. Most broad bands in the UV are attributed to electronic defects in the fluorite lattice, whereas sharp emissions are attributed to intra-ion energy cascades in trivalent lanthanides. Lanthanides are accommodated in fluorite by substitution for Ca<sup>2+</sup> coupled with interstitial F<sup>−</sup>, O<sup>2−</sup> (substituting for F<sup>−</sup>) and a variety of electronic defect structures which provide local charge balance. The chondrite-normalised lanthanide profiles show that fluorite accommodates a greater proportion of heavy lanthanides (and Y) as the total Rare Earth Element (REE) concentration increases; whereas cell parameters decrease and then increase as substitution continues. Luminescence intensity also goes through a maximum and then decreases as a function of REE concentration. All three datasets are consistent with a model whereby lanthanides initially act as isolated centres, but, beyond a critical threshold (~ 1000 ppm), cluster into lanthanide-rich domains. Clustering results in shorter REE-O bond distances (favouring smaller heavier ions), a larger unit cell but more efficient energy transfer between lanthanides, thereby promoting non-radiative energy loss and a drop in the intensity of lanthanide emission.</p></div>\",\"PeriodicalId\":20132,\"journal\":{\"name\":\"Physics and Chemistry of Minerals\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.2000,\"publicationDate\":\"2023-04-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://link.springer.com/content/pdf/10.1007/s00269-023-01239-4.pdf\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Physics and Chemistry of Minerals\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s00269-023-01239-4\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MATERIALS SCIENCE, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01239-4","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
Lanthanide and yttrium substitution in natural fluorite
Fluorite is one of the most common minerals in the crust and is of widespread economic importance. It shows strong UV-excited luminescence, variously attributed to defects within the fluorite structure and lanthanide substitutions. We present here a detailed chemical characterisation of a suite of natural fluorite samples, chosen to represent the range of compositions observed in nature. We perform X-ray excited luminescence spectroscopy on the samples as a function of temperature (20–673 K) in the wavelength range 250–800 nm to provide insights into physical defects in the lattice and their interactions with lanthanide substituents in natural fluorite. Most broad bands in the UV are attributed to electronic defects in the fluorite lattice, whereas sharp emissions are attributed to intra-ion energy cascades in trivalent lanthanides. Lanthanides are accommodated in fluorite by substitution for Ca2+ coupled with interstitial F−, O2− (substituting for F−) and a variety of electronic defect structures which provide local charge balance. The chondrite-normalised lanthanide profiles show that fluorite accommodates a greater proportion of heavy lanthanides (and Y) as the total Rare Earth Element (REE) concentration increases; whereas cell parameters decrease and then increase as substitution continues. Luminescence intensity also goes through a maximum and then decreases as a function of REE concentration. All three datasets are consistent with a model whereby lanthanides initially act as isolated centres, but, beyond a critical threshold (~ 1000 ppm), cluster into lanthanide-rich domains. Clustering results in shorter REE-O bond distances (favouring smaller heavier ions), a larger unit cell but more efficient energy transfer between lanthanides, thereby promoting non-radiative energy loss and a drop in the intensity of lanthanide emission.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)