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Synthesis, Characterization, and Consolidation of Si 3 N 4 Obtained from Ammonolysis of SiCl 4
Author(s) -
MAZDIYASNI K. S.,
COOKE CHARLES M.
Publication year - 1973
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1973.tb12440.x
Subject(s) - materials science , amorphous solid , hot pressing , analytical chemistry (journal) , crystallite , nucleation , microstructure , sintering , dielectric , mineralogy , isothermal process , crystallography , composite material , chemistry , metallurgy , physics , optoelectronics , organic chemistry , thermodynamics , chromatography
Thermal decomposition of silicon diimide, Si(NH) 2 , in vacuum resulted in very‐high‐purity, fine‐particle‐size, amorphous Si 3 N 4 powders. The amorphous powder was isothermally aged at 50° to 100° intervals from 1000° to 1500°C for phase identification. Examination of ir spectra and X‐ray diffraction patterns indicated a slow and gradual transition from an amorphous material to a crystalline α‐phase occurring at 1200°C for >4 h and/or 1300° to 1400°C for 2 h. As the temperature was increased to ≥1450°C for 2 h, the crystalline β‐phase was observed. Phase nucleation and crystallite morphology in this system were studied by electron microscopy and electron diffraction combined with TG as functions of temperature for the inorganic polymer starting materials. Powders prepared in this manner with 4 wt% Mg 3 N 2 added as a sintering aid were hot‐pressed to high‐density fine‐grained bodies with uniform microstructures. The optimum hot‐pressing condition was 1650°C for 1 h. Silicon concentration steadily increased as the hot‐pressing temperature or time was increased. A method for chemical etching for high‐density fine‐grained Si 3 N 4 is described. Electrical measurements between room temperature and ∼500°C indicated dielectric constant and tan δ values of 8.3±0.03 and 0.65±0.05×10 −2 , respectively.