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Accurate Determination of Unit-Cell Parameters using Conventional X-Ray Powder Diffractometry

Published online by Cambridge University Press:  06 March 2019

Hideo Toraya
Affiliation:
Ceramics Research Laboratory, Nagoya Institute of Technology Asahigaoka, Tajimi 507, Japan
William Parrish
Affiliation:
IBM Research Division, Almaden Research Center 650 Harry Road, San Jose, CA 95120-6099, USA
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Abstract

A procedure for the accurate determination of unit-cell parameters using conventional Xray powder diffractometry is described. Two important factors in the procedure are: 1) the use of high-resolution-type diffractometer, which can suppress the axial beam divergence and thus gives nearly symmetric diffraction profiles in the low 2θ region and 2) the use of a new algorithm for systematic peak shift correction during the least-squares determination of unit-cell parameters of a sample with an internal standard [Toraya & Kitamura (1990). J. Appl. Cryst. 23 , 282-285]. The procedure has been tested by measuring successively the unit-cell parameter of W, CeO2, and Si in three mixtures, Si+W, W+CeO2, and CeO2+Si: the unit-cell parameter of W, which was first determined by using NIST SRM 640b Si powder as an internal standard reference material, was used as a standard reference value to determine the unit-cell parameter of CeO; in the next W+CeO2 mixture, and so on. The difference between the end value of observed Si unit-cell parameters and the starting value of 5.430940(35) Å were just 1 to 5 p.p.m. High accuracy is attainable in measuring the uni-cell parameters even with the conventional powder diffractometry provided with the nearly symmetric diffraction profile and the algorithm for peak shift correction used in the present study.

Type
VI. XRD Instrumentation, Techniques and Reference Materials
Copyright
Copyright © International Centre for Diffraction Data 1991

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