Determination of thermal expansion of germanium, rhodium and iridium by X-rays

The lattice parameters of germanium, rhodium and iridium were measured with a Unicam 19 cm high-temperature powder camera; the following equations represent the results: Ge: at = 5.6569 + 34.22 × 10−6t + 10.17 × 10−9t2 − 0.66 × 10−12t3, Rh: at = 3.8026 + 29.27 × 10−6t + 10.49 × 10−9t2 + 0.54 × 10−12t3, Ir: at = 3.8383 + 23.52 × 10−6t + 4.92 × 10−9t2 + 0.89 × 10−12t3. Thermal expansion coefficients and Grüneisen parameters were also calculated.