X-Ray diffraction on large single crystals using a powder diffractometer

TL;DR

This paper presents a method for accurately measuring lattice parameters of large single crystals using a standard powder diffractometer, focusing on correction techniques and alignment optimization for quick, precise results.

Contribution

It provides a detailed procedure for single crystal lattice parameter measurement with a powder diffractometer, including correction and alignment strategies for high accuracy.

Findings

Accurate lattice parameter measurement achievable within minutes.

Effective correction for sample height errors in Bragg-Brentano geometry.

Method applicable to crystals from 200 μm to several millimeters.

Abstract

Information on the lattice parameter of single crystals with known crystallographic structure allows for estimations of sample quality and composition. In many cases it is suffcient to determine one lattice parameter or the lattice spacing along a certain, high-symmetry direction, e.g. in order to determine the composition in a substitution series by taking advantage of Vegard's rule. Here we present a guide to accurate measurements of single crystals with dimensions ranging from 200 $\mu$m up to several millimeter using a standard powder diffractometer in Bragg-Brentano geometry. The correction of the error introduced by the sample height and the optimization of the alignment are discussed in detail. In particular for single crystals with a plate-like habit, the described procedure allows for measurement of the lattice spacings normal to the plates with high accuracy on a timescale of minutes.