Masters Theses

Jen-Kuan Yau

Abstract

"The X-ray method of analyzing for size and strain using powder diffraction profiles is a convenient way for evaluating metals [1, 2, 3, 4], thin films [5, 6] and ceramic powders [7, 8, 9] this method permits one to obtain larger scale information from the samples than any other method. Also, the size and strain in the crystallites of the samples should be considered when doing other X-ray diffraction analyses, e.g., crystal structure refinement and quantitative analysis. Therefore, the objective of this study was to investigate 1) the contribution of the crystallite size and strain to the X-ray powder diffraction profiles, 2) the method to determine these properties, and 3) their application on several phases of interest to ceramists.

The contributions from small crystallite size and strain to the observed diffraction line shape were investigated with respect to the nature and angular dependence of 2θ. The SHADOW profile analysis system [10] was used to perform the size and strain analysis based on separating the instrumental contributions from the sample contributions. A program to perform the RIETVELD [11, 12] pattern-fitting structure-refinement using powder diffraction data was modified to simultaneously perform the structural refinement, and size and strain analysis.

This study has shown that the contributions to line broadening, as a result of small crystallite size and strain, in both Si and Al metals, are Lorentzian in nature. Previous to this study, it was commonly believed that only the size broadening contribution was Lorentzian while the strain contribution was Gaussian in nature [13]. Furthermore, it is evident from the results obtained from program SHADOW that the particle size and strain contributions are best described anisotropically. A study of La-doped SrTi03 with the modified RIETVELD program gave the strain values of the samples and showed that these values are related to the doping concentration and the oxygen partial pressure in which the samples were fired.

Also, the anisotropic nature should be taken into consideration for improving the fitting of the pattern by the RIETVELD method"--Abstract p. ii

Advisor(s)

Scott A. Howard

Committee Member(s)

Robert E. Moore
William Joseph James

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Ceramic Engineering

Publisher

University of Missouri--Rolla

Publication Date

Spring 1988

Pagination

x, 68 pages

Note about bibliography

includes bibliographical references (pages 62-67)

Rights

© 1988 Jen-Kuan Yau, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Thesis Number

T 5697

Print OCLC #

18253291

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