Preparation and Some Properties of Nanostructural Rare Earth Nitrides by Using the Reaction of Hydrides with Ammonia

Abstract

By the use of the thermal decomposition of rare earth (RE) amides to nitrides, the preparation of nanostructural RE nitrides (CeN, PrN, NdN, SmN, GdN, TbN, DyN, HoN and ErN) was extensively studied in search of optimal conditions. In this method, the preparation of amides as an effective precursor for the nitrides was similarly of importance; the amide was here prepared by high-pressure reactions of RE hydrides with ammonia in an autoclave or reactive ball milling of the RE hydrides and ammonia. CeN, PrN, NdN and SmN were successfully prepared by the thermal decomposition of the RE amides or amide-like compounds formed by the reaction of the dihydrides with ammonia, whereas GdN, TbN, DyN, HoN and ErN were not obtained in this way. The dihydrides of gadolinium, terbium, dysprosium, holmium and erbium were generally too stable to react with ammonia to form the amides compared to those of cerium, praseodymium, neodymium and samarium. In the preparation of CeN, PrN and SmN, the amide precursors obtained by the autoclave reaction of the dihydrides with ammonia yielded nanostructural nitrides with higher surface areas (3.9-5.9 m2/g), compared to those obtained by the reactive ball milling method.