Microstructure Determined By X-Ray Diffraction Peak Profile Analysis: a Fingerprint in Archaeology

Abstract

Crystallite size and size-distribution and lattice distortions, often called size and strain, are two fundamental aspects of the microstructure of crystalline materials. Broadened X-ray diffraction peak profiles can be evaluated in terms of these microstructure features. Size-distribution is given by the median and the variancemand a, of the size-distribution function. Strain is given as the density and the arrangement parameter of dislocations, p andMStrain anisotropy, a fundamental feature in powder diffraction,is accounted for by the dislocation contrast factors providing the fifth parameter,q,in the case of cubic crystals.The five parameters:m,σ,p,Mandqprovide a fingerprint of themicrostructureor thestateof the material. PbS (galena) is a major component in ancient Egyptian eye make-up[1]Powder diffractogrammes of geological PbS and PbS in archaeological eye make-up specimens were measured at the ESRF Grenoble synchrotron source with high resolution and high peak to background ratios providing the microstructure parameters [2,3].Themicrostructuresof artificially ground and heated geological PbS have been compared with themicrostructuresof PbS in the archaeological specimens[2, 3].The comparison enabled to conclude about the manufacturing procedures of eye make-up used by ancient Egyptians.