Low temperature solvothermal routes for synthesis of crystalline group 13 and transition metal nitrides via energetic precursor decomposition.

摘要

This dissertation describes the successful utilization of solvothermal methods, mainly in toluene, for the syntheses and characterization of some metastable binary crystalline group 13 and crystalline first row transition metal nitride micro- and nanoparticles synthesized by the decomposition of metal azide. The energetic metal azide intermediate formation and decomposition processes resulting from the reaction between an efficient nitrogen source, sodium azide, with related metal halides produces metal nitrides at low temperature (below 300°C).; The nitride products were studied using various analytical methods; for instance, diffraction, microscopic and various spectroscopic, and other chemical and thermal analytical methods.; Semiconducting luminescence materials were synthesized; for example, nanocrystalline wurtzite InN (Eg = 1.7 eV) from 280°C reaction and wurtzite GaN was crystallized by a post-reaction annealing process. Both of these nitrides were synthesized as an aggregation of the nanoparticles. Lower temperature in toluene and hexadecane systems favorably produced cubic phase mixed InN products, having solvent influenced morphologies. The synthesized ternary metal nitrides, Ga-In-N, showed some evidence of binary metal nitride composites and solid-solution products.; Well-crystallized non-magnetic cubic anti-ReO3 unit cell structured Cu3N was synthesized at very low temperature, having cubic shape of particle aggregation, while the ferromagnetic hexagonal Ni3N was synthesized with smaller (∼20 nm) nanoparticle aggregations. The formation mechanism of nitrides from precursors via azide intermediates was successfully probed through the XRD study of the Cu3N formation. Magnetic Cu 3N was synthesized using NiBr2/CUCl2 mixture, a possible nitrogen centered Cu2NiN2. Strongly ferromagnetic nanocrystalline, &egr;-Fe2N, was also synthesized, as well as various well crystallized phases of magnetic manganese nitrides. These latter nitrides include paramagnetic theta-MnN and a weakly ferromagnetic mixture of eta-Mn 3N2 with &egr;-Mn4N that were synthesized through a well-stirred and precursor pellet reaction, respectively. All of the produced manganese nitride materials showed wire or rod natures of morphologies.; All of the produced crystalline materials from the solvothermal reaction in solvents have relative thermal metastability with organic surface capping agents resulting from reaction with solvents. These organic coatings might improve stability of isolated intermediates and the metastable products in air relative to unstabilized metal nitride particles.