IC Determination of Fluoride and Chloride in Silicon Nitride After Pyrohydrolysis

IC was applied to the determination of fluoride and chloride in silicon nitride after pyrohydrolysis. Sample of silicon nitride was pyrohydrolyzed at 1 050 ℃, and the volatile fluoride and chloride produced were absorbed by sodium hydroxide solution forming anions of F- and Cl- in solution, and determined by ion chromatography. 8.0 mmol·L-1 Na2CO3-1.0 mmol·L-1 NaHCO3 mixed solution was used as eluant, and restraining conductance detector was used in determination. Linearity ranges of F- and Cl- found were between 0.10-1.00 mg·L-1 and between 1.00-10.00 mg·L-1 with detection limits (3σ) of 0.017, 0.026 mg·L-1, respectively. The proposed method was applied to the analysis of silicon nitride sample, giving results in consistency with the values obtained by EDXRFS, and values of RSD′s (n=7) found were all less than 4.0%. Test for recovery was performed by standard addition method, giving values of recovery in the range of 84.5%-106%.