Precision lattice parameters and the coefficients of thermal expansion of hexagonal germanium dioxide

With a Unicam 19 cm high-temperature powder camera, precision lattice parameters of hexagonal germanium dioxide have been determined at various temperatures in the range 36 to 516 °C by the X-ray method. From these data the coefficients of thermal expansion have been evaluated by a graphical method. The temperature dependence of the coefficients of thermal expansion, α_|| and α_⊥, parallel and perpendicular to the principal axis respectively, are represented by the following equations:

where T is the numerical value of the temperature expressed in °C. The thermal expansion of hexagonal GeO₂ has been compared with that of the isomorphous α-quartz and the polymorphous tetragonal rutile-type GeO₂.