Directional Dilatation of Crystal Lattices at Elevated Temperatures

The X‐ray measurement of lattice parameters of crystals at elevated temperatures provides a means of determining the true thermal expansion of a crystal. In this investigation, a furnace in which temperatures above 1200°C. could be accurately maintained and a specially designed circular back‐reflection X‐ray camera were employed in measuring the thermal dilatation of crystals representative of the cubic, hexagonal, rhombohedral, and tetragonal systems. Thermal‐expansion values up to 1200°C. are reported for magnesia, alumina, zinc oxide, rutile, beryllia, calcium oxide, and strontium oxide and for magnesia‐alumina, magnesia‐chrome, zinc‐alumina, and zinc‐chrome spinels.