{"id":488,"date":"2020-04-23T19:52:41","date_gmt":"2020-04-23T19:52:41","guid":{"rendered":"https:\/\/cms.eas.ualberta.ca\/xrd\/?page_id=488"},"modified":"2022-12-13T18:45:42","modified_gmt":"2022-12-13T18:45:42","slug":"applications","status":"publish","type":"page","link":"https:\/\/cms.eas.ualberta.ca\/xrd\/applications\/","title":{"rendered":"Applications"},"content":{"rendered":"
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Phase Identification<\/a>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Quantitative XRD<\/a>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Semi-Quantitative XRD (RIR)<\/a>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0Percent Crystallinity\/Crystallite Size<\/a>
\n<\/a><\/h3>\n

<\/h3>\n

Phase Identification\"\"<\/h3>\n

Phases are identified by taking an unknown sample's diffraction pattern and search\/matching it against an XRD database. Phases are matched one by one until all the diffraction peaks in a sample have been identified.<\/p>\n

Conditions\/Assumptions<\/p>\n

    \n
  1. Crystallites are randomly orientated<\/li>\n
  2. Sample has been sufficiently ground<\/li>\n
  3. Sample has been properly mounted<\/li>\n
  4. The sub sample given to the technician is representative of the whole sample<\/li>\n<\/ol>\n

    Limitations<\/p>\n

      \n
    1. The limit of detection on the XRD is between 1 - 5 wt% depending on the quality of sample preparation and sample type<\/li>\n
    2. You cannot tell the elemental composition quantitatively with powder XRD, other analytical techniques are needed for this i.e. XRF, EPMA<\/a>, SEM<\/a><\/li>\n
    3. You cannot resolve phases with identical structures and similar atomic sizes, additional information about the elemental composition are needed to resolve this<\/li>\n
    4. Preferred Orientation - can minimize this with proper sample preparation and mounting, but can still be a factor distorting intensity ratios<\/li>\n
    5. The more phases there are, the more difficult it is to properly identify<\/li>\n
    6. The lower the abundance of a phase the more difficult it is to identify<\/li>\n<\/ol>\n

      <\/a><\/p>\n

      Quantitative XRD - Rietveld Refinement<\/h2>\n

      The sample's diffraction pattern is modeled using a least squares refinement to determine the amount of each phase contributing to the diffraction pattern, giving a semi-quantitative estimate of the phase abundances. Clays are particularly tricky to model due to the fact that their structure changes with varying conditions (i.e. humidity) and require extra care.<\/p>\n

      Conditions\/Assumptions<\/p>\n

        \n
      1. That you have an ideal diffraction pattern of that sample (No preferred orientation, crystallites are randomly orientated, 1\u00a0\u03bcm particle size, perfect sample mounting, high quality scan conditions)<\/li>\n
      2. That all the phases in the sample have been identified and identified correctly<\/li>\n
      3. Detailed structure information is available for all the phases identified<\/li>\n<\/ol>\n

        Limitations<\/p>\n

          \n
        1. The more phases present in the sample, the more difficult the refinement becomes<\/li>\n
        2. Phases below the limit of detection are not included in the analysis<\/li>\n
        3. There is 2 wt% error associated with any of the estimates provided<\/li>\n<\/ol>\n

          \"\"
          \n          <\/a><\/p>\n

          Semi-Quantitative XRD - Reference Intensity Ratios<\/h2>\n

          Uses the ratio between intensity of the strongest peak of your identified phase compared and the strongest peak of a standard (corundum is internationally used) in a 50 - 50 mixture (I\/Ic<\/sub>) to determine the abundance of that phase in a sample. The ratio I\/Ic<\/sub>\u00a0can be either experimentally derived or calculated theoretically. The ICDD has published the I\/Ic<\/sub>\u00a0ratios for over 10000 materials. Therefore the abundances of phases within a sample can be determined without an internal standard or with extensive modelling i.e. Rietveld Refinement.<\/p>\n

          Conditions\/Assumptions<\/p>\n

            \n
          1. That there is minimal to no preferred orientation<\/li>\n
          2. That the crystallite size is the same for all the phases within the sample<\/li>\n
          3. That there is a constant diffraction volume<\/li>\n<\/ol>\n

            Limitations<\/p>\n

              \n
            1. Cannot resolve overlapping peaks as well as a Rietveld Refinement<\/li>\n
            2. Cannot model preferred orientation or instrumental parameters, a Rietveld Refinement can<\/li>\n
            3. Larger error associated with RIR compared to a Rietveld Refinement<\/li>\n<\/ol>\n

              <\/a><\/p>\n

              Percent Crystallinity\"\"<\/h2>\n

              The relative amount of amorphous versus crystalline material within a sample is determined by performing a profile fitting and comparing the area attributed to the amorphous material to that of the crystalline material.<\/p>\n

              Conditions\/Assumptions<\/p>\n

                \n
              1. That the amorphous and crystalline material reflect x-rays with equal efficiency<\/li>\n<\/ol>\n

                Limitations<\/p>\n

                  \n
                1. Amorphous materials do not always reflect x-rays as efficiently as crystalline material<\/li>\n
                2. The less amorphous material there is, the larger the error on the amorphous content estimation<\/li>\n<\/ol>\n

                  <\/a><\/p>\n

                  Crystallite Size<\/h2>\n

                  The width of the peaks in a diffraction pattern are controlled by the crystallite size for that phase. The smaller the crystallites the broader the peaks become. Crystallite sizes for phases within a sample can be estimated by using the Sherrer Equation:<\/p>\n

                  Conditions\/Assumptions\"\"<\/p>\n

                    \n
                  1. Assumes spherical crystallites<\/li>\n
                  2. Assumes a normal crystallite distribution<\/li>\n<\/ol>\n

                    Limitations<\/p>\n

                      \n
                    1. Does not provide accurate dimensions of a non spherical crystallite<\/li>\n<\/ol>\n

                       <\/p>\n<\/div>\n<\/div><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"

                      Phase Identification\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Quantitative XRD\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Semi-Quantitative XRD (RIR)\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0Percent Crystallinity\/Crystallite Size Phase Identification Phases are identified by taking an unknown sample’s diffraction pattern and search\/matching it against an XRD database. Phases are matched one by one until all the diffraction peaks in a…<\/p>\n","protected":false},"author":34,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"home-panels.php","meta":{"footnotes":""},"class_list":["post-488","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/pages\/488","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/users\/34"}],"replies":[{"embeddable":true,"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/comments?post=488"}],"version-history":[{"count":33,"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/pages\/488\/revisions"}],"predecessor-version":[{"id":666,"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/pages\/488\/revisions\/666"}],"wp:attachment":[{"href":"https:\/\/cms.eas.ualberta.ca\/xrd\/wp-json\/wp\/v2\/media?parent=488"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}