Journal of Applied Crystallography

Volume 46, Part 3 (June 2013)

laboratory notes

J. Appl. Cryst. (2013). 46, 823-825    [ doi:10.1107/S0021889813005955 ]

A cautionary tale on the use of GE-7031 varnish: low-temperature thermal expansion studies of ScF3

C. R. Morelock, M. R. Suchomel and A. P. Wilkinson

Abstract: GE-7031 varnish, a commonly used low-temperature adhesive and electrical insulator owing to its high thermal conductivity and mechanical strength at low temperatures, was used as a sample matrix for low-temperature powder X-ray diffraction measurements of the negative thermal expansion (NTE) material ScF3. When ScF3 powder was mixed with GE-7031 varnish, an unexpected cubic to rhombohedral phase transition in the ScF3 sample was observed at ~50 K, and it exhibited smaller low-temperature unit-cell volumes than samples without the varnish matrix. Experimental observations and quantitative estimates suggest that these anomalies are the result of stress induced by a thermal expansion mismatch between the varnish matrix (large positive coefficient of thermal expansion, CTE) and ScF3 (quite large negative CTE). The use of GE-7031 varnish as a sample matrix for low-temperature measurements should be approached with caution if a large thermal expansion mismatch is expected.

Keywords: GE-7031 varnish; scandium trifluoride; low-temperature X-ray diffraction; powder X-ray diffraction; negative thermal expansion; composites.

pdfdisplay filedownload file

Portable Document Format (PDF) file
[ doi:10.1107/S0021889813005955/ks5362sup1.pdf ]
Supplementary material


To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

 bibliographic record in  format

  Find reference:   Volume   Page   
  Search:     From   to      Advanced search

Copyright © International Union of Crystallography
IUCr Webmaster