Silicon nitrides: Some physico‐chemical properties

Silicon nitride has been prepared by heating pure silicon in purified nitrogen at 1450°. X‐ray studies showed the presence of two nitrides, and a method was therefore devised to separate them. Although these nitrides differ in their crystal structure, they have the same compositions, corresponding to Si3N4. A few chemical tests were performed on finely divided silicon nitride prepared at or above 145°. Several alloys containing various proportions of silicon were nitrided under different conditions, and the X‐ray diffraction patterns of the nitrides extracted from these alloys were found to be in complete agreement with that of α‐Si3N4. The diffraction lines obtained from the nitrided alloy prior to any chemical treatment gave nitride lines which did not correspond to those of the α‐Si3N4 or β‐Si3N4.