Preparation method of micro-chlorine high-alpha-phase silicon nitride powder

The invention relates to the technical field of preparation of silicon nitride ceramic materials, in particular to a preparation method of micro-chlorine high-alpha-phase silicon nitride powder, which comprises the following steps: (1) reacting liquid ammonia and gaseous silicon tetrachloride in a molar ratio of 1: (10-100) at-60-10 DEG C for 0.5-6 hours to obtain a suspension; (2) carrying out primary filtration on the suspension, and dechlorinating a filter cake by adopting a dechlorinating solution; a preparation method of the dechlorination liquid comprises the following steps: adding 3-12 parts of 4-dimethylaminopyridine, 10-20 parts of tetramethylguanidine, 3-8 parts of triethylene diamine and 1-8 parts of tetramethylethylenediamine into 100-180 parts of n-hexylamine, and reacting at the stirring speed of 1-300r/min and the temperature of 30-70 DEG C for 3-10 hours; and (3) carrying out secondary filtration on the dechlorinated reaction liquid, and calcining a filter cake for 0.5-48 hours in an inert re