NITRIDATION REACTION OF TANTALUM PENTACHLORIDE IN THE PRESENCE OF MAGNESIUM

The nitridation process of TaCl5 with Mg (2:5 in molar ratio) has been investigated at 200-degrees approximately 1050-degrees-C under a nitrogen gas flow. The tantalum nitrides of beta-, gamma-, theta- and epsilon- phases were synthesized according to their temperatures by the diffusion and occlusion of nitrogen in Ta lattices, after metallic Ta was formed by the reduction of TaCl5 with Mg above 400-degrees-C. In the reduction-nitridation of the TaCl5-Mg-N2 system, the formation reactions such as TaCl5 --> metallic Ta --> TaN0.1 (beta-phase) --> Ta2N (gamma-phase) --> TaN0.8 (theta-phase) --> TaN1.0 (epsilon-phase) proceeded stepwise accompanying a phase transition with increasing temperature. The phases of tantalum nitrides had the most stable structure at each temperature:TaN0.1, Ta2N and TaN0.8 were formed at 400-degrees-C, 600-degrees-C and 800-degrees-C, respectively.