The vacuum microbalance method, as well as petrographic and X-ray phase analyses, were used to investigate oxidation at 700 to 1200C under oxygen pressures of 0.1 to 740Torr. It was established that the material was highly resistant to oxidation in oxygen at up to 1200C. The protective properties of the scale were determined by the peculiarities of the process of internal oxidation, during which a lower lanthanum boride, LaB4, was observed to be enveloped by a vitreous B2O3 phase.

Investigation of High-Temperature Oxidation of Lanthanum Hexaboride in Oxygen and the Effect of Internal Oxidation on the Protective Properties of the Scale. Lavrenko, V.A., Glebov, L.A., Lugovskaya, Y.S., Frantsevich, I.N.: Oxidation of Metals, 1973, 7[2], 131-9