Synthesis of Metastable Co4N, Co3N, Co2N, and CoO0.74N0.24 from a Single Azide Precursor and Intermediates in CoBr2 Ammonolysis
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY(2016)
摘要
Metastable cobalt nitrides Co4N, Co3N, Co2N, and cobalt oxide nitride CoO0.74N0.24 were synthesized by ammonolysis of one single metastable azide precursor, [Co(NH3)(5)N-3]Cl-2, in high purity by controlled variation of the reaction conditions (temperature, duration, gas atmosphere, and flow rate). The alternative route towards cobalt nitrides by ammonolysis of CoBr2 proceeds via [Co(NH3)(6)]Br-2 and Co(NH3)(2)Br-2 to exclusively yield Co3N. For Co3N1.1 a complex magnetic behavior is observed: dominating ferromagnetic ordering at low temperatures and a small coercive field of 10 mT. Co2N orders antiferromagnetically below 10 K. Electronic structure calculations [DFT, generalized-gradient approximation (GGA)+U] on CoO0.75N0.25 reveal that the experimentally observed rock-salt structure is less stable than the sphalerite-type polymorph by about 30 kJ mol(-1) and possesses an antiferromagnetically ordered ground state.
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关键词
Cobalt,Nitrides,Magnetic properties,Metastable compounds,Density functional calculations
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