Thermal expansion of chromium (Cr) to melting temperature

In situ x-ray data on molar volumes of chromium have been collected over the temperature range from 300 K to melting. The sample was heated to melting by passing an electrical current through the sample (the technique of electrical resistance wire heating). The sample consists of a tungsten wire as a heater and a mixture of Cr and W powder, which is placed in a hole of 250 mu m diameter. Tungsten was used as an internal standard for temperature determination. In order to prevent the specimen from oxidation, the experiments were carried out in an argon flow. Unit cell parameters of Cr at different temperatures were calculated using (110), (200), (211), and (220) reflections. Precision of determination of lattice parameter is 10(-4) A at 300 K and 5 10(-4) A at 2000 K. Thermal expansion of Cr increases rapidly at temperatures higher than 1200 K. The linear thermal expansion (alpha) of chromium between 300 and 2130 K is given by: alpha = 1.220(5) 10(-5) - 1.150(6) 10(-8) T + 1.132(8) 10(-6) T-2 - 0.507(7)/T-2 (T, K). In our experiments, Cr melted between 2120 and 2150 K.