{"id":16,"date":"2024-04-04T04:31:16","date_gmt":"2024-04-04T01:31:16","guid":{"rendered":"https:\/\/sisu.ut.ee\/heritage-analysis\/42-xrf\/"},"modified":"2024-07-18T14:35:46","modified_gmt":"2024-07-18T11:35:46","slug":"42-xrf","status":"publish","type":"page","link":"https:\/\/sisu.ut.ee\/heritage-analysis\/42-xrf\/","title":{"rendered":"4.2. XRF and XRD"},"content":{"rendered":"<div style=\"height:30px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<p>In this lecture, two methods \u2013\u00a0<strong>X-ray fluorescence spectroscopy (XRF) <\/strong>and\u00a0<strong>X-ray diffraction (XRD)<\/strong><strong>\u00a0analysis <\/strong>\u2013\u00a0will be discussed together. During the lecture, sample preparation will be described, and practical tips for the analysis as well as examples will be given. XRF (more recently also portable XRF) is (together with SEM-EDS) among the most important methods for determining the elemental composition\u00a0of cultural heritage materials.\u00a0XRD is valuable for analysing the structure of\u00a0crystalline materials, i.e. the spatial arrangement of atoms in crystals and identifying the materials on the basis of the structure. XRD is applicable to\u00a0 minerals, clays etc.\u00a0\u00a0<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span style=\"color: #b22222;\">1. General aspects of X-Ray Diffraction\u00a0and X-Ray Fluorescence<\/span><\/h2>\n\n\n\n<p>In the following video, the general theoretical aspects of XRD and XRF are discussed.<\/p>\n\n\n\n<p><\/p><div class=\"ratio ratio-16x9 mb-3\"><div class=\"video-placeholder-wrapper video-placeholder-wrapper--16x9\">\n\t\t\t    <div class=\"video-placeholder d-flex justify-content-center align-items-center\">\n\t\t\t        <div class=\"overlay text-white p-2 w-100 text-center d-block justify-content-center align-items-center\">\n\t\t\t            <div>To view third-party content, please accept cookies.<\/div>\n\t\t\t            <button class=\"btn btn-secondary btn-sm mt-1 consent-change\">Change consent<\/button>\n\t\t\t        <\/div>\n\t\t\t    <\/div>\n\t\t\t<\/div>\n<\/div>\n\n\n\n<div style=\"height:30px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\"><em><span style=\"color: #b22222;\">Description of\u00a0X-ray fluorescence spectroscopy (XRF)<\/span><\/em><\/h2>\n\n\n\n<p><\/p>\n\n\n\n<p>All X-ray fluorescence spectrometers share the common principle that can be presented as follows:<\/p>\n\n\n\n<p><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Polychromatic (i.e. containing photons with different energies\/wavelengths)\u00a0X-rays are directed onto the sample. Polychromaticity of the radiation is needed in order to enable, as far as possible, detecting the atoms of all the different elements that are present in the sample.<\/li>\n\n\n\n<li>The X-ray photons ionise atoms in the surface layer\u00a0of the sample by ejecting an electron from the inner electron shells of the atoms.\n<ul class=\"wp-block-list\">\n<li>Depending on the situation, the thickness of the surface layer that produces the secondary X-rays can range from a few \u03bcm (determining light elements in a sample composed mostly of heavy elements) to hundreds of \u03bcm (determining heavy elements in a sample composed mostly of light elements).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>The formed positive ions are highly excited (because of the vacancy in an inner shell) and relax very fast. Relaxation consists of two simultaneous processes: filling the vacancy with an electron from one of the next shells and emitting the released energy as a secondary X-ray photon.<\/li>\n\n\n\n<li> These emitted secondary X-rays are the ones that are detected by the XRF instrument and consist of photons with energies (and wavelengths) that are characteristic to the elements that are present in the sample. Every element emits X-rays with a characteristic set of photon energies and wavelengths.<\/li>\n<\/ol>\n\n\n\n<div class=\"wp-block-group is-vertical is-layout-flex wp-container-core-group-is-layout-8cf370e7 wp-block-group-is-layout-flex\">\n<p><\/p>\n\n\n\n<p>Most XRF spectrometers are capable of detecting the <strong>elements<\/strong> of the periodic table from <strong>sodium to uranium<\/strong>. However, the limit of detection increases rapidly as the atomic number decreases below that of sodium.<\/p>\n\n\n\n<p>X-ray fluorescence spectrometers of two design principles are available: <strong>wavelength dispersive X-ray fluorescence spectrometers (WD-XRF)<\/strong> and <strong>energy dispersive X-ray fluorescence spectrometers (ED-XRF)<\/strong>. WD-XRF produces a spectrum by using a crystal monochromator to diffract the fluorescent X-rays, a single wavelength at a time, onto a detector that measures their intensity. ED XRF permits the fluorescence radiation emitted at all wavelengths to reach the detector simultaneously and uses a pulse-height discriminator to electronically classify the energy of the X-ray photons that strike the detector.\u00a0Both designs have their advantages and limitations and are widely used.<\/p>\n\n\n\n<p><\/p>\n\n\n\n<p><\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\"><em><span style=\"color: #b22222;\">Description of\u00a0X-ray Diffraction (XRD)<\/span><\/em><\/h2>\n\n\n\n<div class=\"wp-block-group is-vertical is-layout-flex wp-container-core-group-is-layout-8cf370e7 wp-block-group-is-layout-flex\">\n<p>The XRD method gives information about the spatial structure of <strong>crystalline materials<\/strong>.\u00a0XRD can analyse only crystalline substances (in the case of a mixture \u2013 the crystalline components)\u00a0and provides information on their structures, phases, preferred crystal orientations (texture), and other structural parameters. Generally, X-ray diffraction is based on constructive interference of monochromatic X-rays and a crystalline sample. Each crystalline substance has a unique repeating three-dimensional array of atoms and produces a unique X-ray diffraction pattern. Diffraction patterns can be used as \u201cfingerprints\u201d for the identification of crystalline phases.<\/p>\n\n\n\n<p>X-ray diffraction experiments are performed by irradiating a crystalline sample with a beam of X-rays, X-rays interact with the sample in such a way that the X-rays are\u00a0diffracted from the atomic planes. Because of the interference of the, rays only those that are emitted in\u00a0certain directions\u00a0survive (constructive interference). The remaining rays are destroyed by destructive interference.\u00a0<\/p>\n<\/div>\n\n\n\n<p>The interaction of the incident rays with\u00a0a certain set of atomic planes produces constructive interference (and a diffracted ray) when the interference angle 2<em>\u0398<\/em> satisfies the following\u00a0conditions, known as\u00a0<strong>Bragg\u2019s Law<\/strong>, which\u00a0is defined as follows:<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-text-align-center\"><span style=\"color: #000000;\"><strong>\u00a0<\/strong>n\u03bb=2d sin <em>\u03b8<\/em><\/span><\/h2>\n\n\n\n<p>where,\u00a0<em>n<\/em> is an integer number (known as diffraction order), \u03bb is the wavelength of the used radiation, and <em>d<\/em> is the distance between the atomic planes (lattice spacing).<\/p>\n\n\n\n<div class=\"wp-block-group is-vertical is-layout-flex wp-container-core-group-is-layout-8cf370e7 wp-block-group-is-layout-flex\">\n<p>This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample.\u00a0In real crystals, there are numerous atomic planes and thus also numerous angles 2<em>\u0398<\/em> that satisfy the Bragg\u2019s law.<\/p>\n\n\n\n<p>Each of these angles will produce a maximum (peak) on the diffraction picture (<strong>diffractogram<\/strong>), and for every mineral, there exists a set of characteristic peaks by which the mineral can be identified (see Fig. 1).\u00a0So, both the diffraction angle and the intensity of each of the diffracted beams (diffraction peaks) are then measured, processed and counted. The intensity of diffracted X-rays is plotted as a function of diffraction angle 2<em>\u03b8<\/em>.<\/p>\n<\/div>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"1523\" height=\"1028\" src=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/difractograms.jpg\" alt=\"\" class=\"wp-image-839\" style=\"width:944px;height:auto\" srcset=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/difractograms.jpg 1523w, https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/difractograms-300x202.jpg 300w, https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/difractograms-1024x691.jpg 1024w, https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/difractograms-768x518.jpg 768w\" sizes=\"auto, (max-width: 1523px) 100vw, 1523px\"><figcaption class=\"wp-element-caption\">Fig. 1. Diffractograms of mineral mixtures.<\/figcaption><\/figure>\n\n\n\n<div class=\"wp-block-group is-vertical is-layout-flex wp-container-core-group-is-layout-8cf370e7 wp-block-group-is-layout-flex\">\n<p class=\"has-text-align-left\">In cultural heritage research powder diffractometers are usually used. For powder diffractometer the sample is powderized in order to ensure that small crystals of all different orientations are present in the sample. For additional randomization, the sample holder is rotated. This arrangement ensures that as a result of the diffraction of a single collimated beam, all possible reflections (corresponding to all possible diffraction angles) can be observed.<\/p>\n\n\n\n<p>The intensities of these reflections are recorded, usually with a charge-coupled device (CCD) image sensor. By scanning the sample through a range of 2<em>\u03b8<\/em>\u00a0angles, all possible reflections will be recorded due to the random orientation of the powdered material.<\/p>\n<\/div>\n\n\n\n<p><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span style=\"color: #b22222;\">2. Analysis with XRD and XRF methods<\/span><\/h2>\n\n\n\n<p><\/p>\n\n\n\n<p>In the following video, Dr Peeter Somelar introduces typical ways of sample preparation for the XRD and XRF analysis.<\/p>\n\n\n\n<p><\/p><div class=\"ratio ratio-16x9 mb-3\"><div class=\"video-placeholder-wrapper video-placeholder-wrapper--16x9\">\n\t\t\t    <div class=\"video-placeholder d-flex justify-content-center align-items-center\">\n\t\t\t        <div class=\"overlay text-white p-2 w-100 text-center d-block justify-content-center align-items-center\">\n\t\t\t            <div>To view third-party content, please accept cookies.<\/div>\n\t\t\t            <button class=\"btn btn-secondary btn-sm mt-1 consent-change\">Change consent<\/button>\n\t\t\t        <\/div>\n\t\t\t    <\/div>\n\t\t\t<\/div>\n<\/div>\n\n\n\n<p>In the following video, Dr Peeter Somelar introduces XRD and XRF instruments and how to perform analysis using these methods.<\/p>\n\n\n\n<p><\/p><div class=\"ratio ratio-16x9 mb-3\"><div class=\"video-placeholder-wrapper video-placeholder-wrapper--16x9\">\n\t\t\t    <div class=\"video-placeholder d-flex justify-content-center align-items-center\">\n\t\t\t        <div class=\"overlay text-white p-2 w-100 text-center d-block justify-content-center align-items-center\">\n\t\t\t            <div>To view third-party content, please accept cookies.<\/div>\n\t\t\t            <button class=\"btn btn-secondary btn-sm mt-1 consent-change\">Change consent<\/button>\n\t\t\t        <\/div>\n\t\t\t    <\/div>\n\t\t\t<\/div>\n<\/div>\n\n\n\n<p>The slides used in the video can be downloaded from\u00a0here:<\/p>\n\n\n\n<div class=\"wp-block-group attached-files-group is-layout-constrained wp-block-group-is-layout-constrained\">\n<div class=\"wp-block-file\"><a id=\"wp-block-file--media-dbb2ec6c-3035-4e1c-9412-0eddb84e211a\" href=\"https:\/\/sisu.ut.ee\/wp-content\/uploads\/sites\/285\/general_aspects_xrd_and_xrf.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">General_aspects_XRD_and_XRF.pdf<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this lecture, two methods \u2013\u00a0X-ray fluorescence spectroscopy (XRF) and\u00a0X-ray diffraction (XRD)\u00a0analysis \u2013\u00a0will be discussed together. During the lecture, sample preparation will be described, and practical tips for the analysis as well as examples will be given. XRF (more recently &#8230;<\/p>\n","protected":false},"author":151,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"class_list":["post-16","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/pages\/16","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/users\/151"}],"replies":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/comments?post=16"}],"version-history":[{"count":5,"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/pages\/16\/revisions"}],"predecessor-version":[{"id":1152,"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/pages\/16\/revisions\/1152"}],"wp:attachment":[{"href":"https:\/\/sisu.ut.ee\/heritage-analysis\/wp-json\/wp\/v2\/media?parent=16"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}