Low temperature synthesis and characterization of pure lanthanum hexaboride nanocrystals

Abstract

This study aims to synthesize very pure form of LaB6 nanocrystals at low temperatures. The synthetic route employed involved low temperature magnesiothermic reduction process of La2O3 with a mixture of Mg, I2 and B2O3 at 90 °C. The powder mixtures were mechanically induced under Ar atmosphere for 3 h and then heat treated. The pure form of nano LaB6 powder produced by this technique is by far the most versatile route for the synthesis of nano-LaB6. From the XRD evidences of the synthesized powders, a correct reaction path for the reduction process has been elucidated. The average particle size of nano powder synthesized was estimated from SEM as well as XRD as 78 ± 12 nm and 61.3 ± 2.0 nm respectively, and the values were found to be in good agreement. The particle size determined by XRD was upon applying the Rietveld refinement method and using isotropic Lorentzian Scherrer particle broadening parameter (LX) of refined peak profiles. From the average size of the particulates and from the specific surface area of LaB6 (1.3 m2/g) as determined by BET method, the number of unit crystals that might have constituted a nano-particulate of size 61.3 ± 2.0 nm was estimated as 105 numbers from the crystallographic information of LaB6.