Precise measurement of the lattice parameters of α-Al2O3in the temperature range 4.5–250 K using the Mössbauer wavelength standard

The lattice parameters of α-Al2O3have been measured in a temperature range from 4.5 to 250 K with a relative accuracy of better than 6 × 10−6. The experimental method uses Bragg backscattering and the recently proposed Mössbauer wavelength standard,i.e.the wavelength λM= 86.025474 (16) pm of the nuclear resonance radiation of57Fe (Shvyd'koet al., 2000), which has previously been applied successfully to measure the lattice parameters of α-Al2O3at temperatures between 286 and 374 K (Shvyd'koet al., 2002). The experimental data in the range from 4.5 to 374 K are consistent with the Debye model of thermal expansion. At 4.5 K, the thermal expansion coefficient is as low as 1.2 (9) × 10−10 K−1in theadirection.