The method of multiphase synthesis of NH₄HfF₅ for accelerator mass spectrometry (AMS) measurement was researched in this paper. After separation and purification progress, the HfO₂ sample was made to NH₄HfF₅ which was measured by AMS with NH₄HF₂ by reaction. The results show that the extraction of α-benzoin oxime was important step for the degression of ¹⁸²W. The beam flux of in NH₄HfF₅ made by multiphase synthesis was three to four times as that made by liquid-phase sysnthesis at the same condition. The sample preparation methods (multiphase synthesis or liquid-phase sysnthesis) have little impact on the ratio of ¹⁸²W/Hf. The ratio of ¹⁸²W/Hf in NH₄HfF₅ was as low as the order of 10^－11 g• g^－1. The structure of NH₄HfF₅ powder was characterized by XRD and XPS. The results show that there were N, Hf and F elements in NH₄HfF₅ powder, and Hf mainly existed in quadrivalent state (＋4).

Key words: accelerator mass spectrometry, NH₄HfF₅, synthesis, characterization