SCHEDULED MAINTENANCE
The development of an approach for the precision determination of thermal strain tensor elements for single crystals using the example of t-Ag0.8Li0.2InSe2†
Abstract
An original approach for the determination of unit cell parameter temperature dependence using a conventional single-crystal X-ray diffractometer is proposed. The approach is based on the calibration of the goniometer equatorial circle segment using the position of several Kα1/Kα2 doublets from reference single crystals. It allows for the refinement of lattice parameters of single crystals with a relative error of less than 10−4. Its capabilities are demonstrated using an example of tetragonal single crystals. The space group, crystal structure, and composition of t-Ag0.8Li0.2InSe2 were determined using single-crystal X-ray diffraction analysis of three small (linear sizes ∼0.1 mm) fragments from a larger (linear sizes up to 10 mm) single-crystal grown using the Bridgman method. The dynamics of the crystal structure changes in the temperature range of 90–500 K were studied. The obvious anisotropy of t-Ag0.8Li0.2InSe2 thermal behavior was shown with an overall increase in the volume of the tetragonal unit cell by 0.51%—parameter a increased by 0.34, while parameter c decreased by 0.17%. The nonlinear dependence of the thermal expansion tensor elements on temperature was determined: α11 × 106 = −4.28 + 0.08T − 1.95 × 10−4T2 and α33 × 106 = −5.59 + 0.01T − 1.97 × 10−5T2.
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