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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.