Katherine Harrington X-Ray Techniques: XRD & XRF 1. XRD and XRF both bo th utilize -rays! but XRD "ro#ides in$or%ation on the crystalline structure o$ co%"ounds! hereas XRF returns data regarding ele%ental co%"osition. XRD can "ro#ide in$or%ation on the "hases o$ a co%"ound! hich %ay ha#e rele#ance to its archaeological inter"retation. inter"retation. For ea%"le! the silicates in clay change "hase at certain $iring te%"eratures! so XRD can "ro#ide in$or%ation about the te%"erature at hich a cera%ic sa%"le as $ired. $ired. XRF! on the other hand! "ro#ides se%i-quantitati#e se%i-quantitati#e concentrations $or a range o$ ele%ents. '. XRD is only use$ul $or analyzing crystalline co%"ounds. co%"ounds. XRD is not a""ro"riate a""ro"riate $or the analysis o$ a%or"hous a%or"hous %aterials. (onsequently! it cannot be used on glass! "lastics! $ibers! and dyestu$$s. ). There are to ty"es o$ XRF %achines! a handheld #ersion and a stationary #ersion. The sa%"le size li%it li%it $or the handheld #ersion is theoretically in$inite. Thus! the handheld XRF is non-destructi#e and non-in#asi#e! "ro#ided the sur$ace o$ the %aterial is un-corroded and does not require require treat%ent "rior to the the analysis. *oth the tableto" XRF and XRD %achines do ha#e sa%"le sa%"le size li%itations. The sa%"le %ust $it into the s%all sa%"le "lat$or%. +,-,D+ 1. +canning electron %icrosco"y "roduces etre%ely high %agni$ication i%ages o$ a sa%"le and is used to $or $or analysis o$ "article "article sha"es. ,nergy dis"ersi#e -ray -ray s"ectrosco"y "ro#ides ele%ental analysis. analysis. The ele%ental analysis can be targeted on a "oint-by-"oint basis or across a transect. '. +, is best a""lied a""lied to %aterials that are structurally or co%"ositionally co%"ositionally heterogeneous. *oth organic and inorganic sa%"les sa%"les can be analyzed! though non%etallic %aterials need to be coated ith a #ery thin layer o$ a conducti#e %aterial to "re#ent bea% distortion and de$lection. The sa%"le %ust $it into the detector and thus %ust be less than ) square centi%eters. t can be either a cross section or a "article. The sa%"le %ust be $lat! and %ay need to be "olished or che%ically etched. ). ,D+ can be used on both conducti#e and nonconducti#e %aterials. t is #ery sensiti#e! but the quality o$ results does not %atch those o$ a dedicated electron %icro"robe! due to constraints o$ geo%etry. /. 0s %entioned %entioned abo#e question '2! non-%etallic %aterials %aterials need to be coated ith a #ery thin layer o$ a conducti#e %aterial to "re#ent bea% distortion and de$lection in +,. The sa%"le %ust be $lat! and %ay need to be e%bedded in resin and "olished or che%ically etched.
Katherine Harrington 3. +,-,D+ is "artially destructi#e in the sense that a s%all sa%"le %ay need to be re%o#ed $ro% a larger ob4ect and that sa%"le %ay need to be coated! etched! or "olished. Hoe#er! the sa%"le does not need to be "ul#erized. 5. +,-,D+ can be used on any ty"e o$ %aterial! "ro#ide the sa%"le is "re"ared correctly. t is %ost use$ul $or heterogeneous %aterials! because it can "ro#ide in$or%ation about changes in sur$ace relie$ and co%"osition. 6. +econdary electron i%ages "ro#ide %agni$ication o$ sur$ace to"ogra"hy. *ac7scattered electron i%ages are "roduced $ro% di$$erences in %aterial co%"osition! so they can sho changes in co%"osition across the sur$ace o$ the sa%"le and enhanced to"ogra"hic detail. ,nergy dis"ersi#e -ray s"ectrosco"y "ro#ides ele%ental analysis.