Silicon 640b SRM (NIST) thermal expansion

An in-situ XRD study of the thermal expansion of the well-known standard material for peak position calibration, Silicon 640b SRM (NIST).

Silicon is one of the most frequently used internal standard materials in powder diffraction applied for peak position calibration. The National Institute of Standards Technology Administration, U.S. Department of Commerce (NIST) supplied the powder diffraction community with two batches of silicon powder of certified lattice parameters, (Standard Reference Material) SRM 640 and later SRM 640b. The thermal expansion of SRM 640b silicon was studied with the Anton Paar HTK 1200 high temperature (HT) chamber.


Experimental and results

Silicon is known to be harmful for the Pt heating band of most widely used HT powder chambers because a low melting PtSi eutectic is formed. In the case of the HTK 1200 the ceramic (alumina) sample holder ideally suits for a high temperature measurement of silicon. The chamber can be well evacuated in order to avoid oxidation of silicon, despite the presence of fibre ce-ramics insulation.

Sample displacement caused by thermal expansion of the sample stage at high temperatures was compensated with the motorized sample positioner according to a previous careful calibration.

The measured temperatures were corrected accord-ing to a previous temperature calibration with several reference materials.

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