Abstract: The experimental results at variant programs of raising temperature are care- fully examined during the synthetic process of ZnP_2 while P and Zn are located at the opposite ends of a sealed evacuated quartz tube. It is found that the phosphorus vapour pressure has an effect on zinc phosphorus formation. When the phosphorus vapour pressure is not high enough, Zn_3P_2 will be formed; When the phosphorus vapour pressure is high enough but lower than 4 atm., both red tetragonal ZnP_2 and black monoclinic ZnP_2 will be formed, and the content of blask ZnP_2 is tend to be increasing with the increment of the phosphorus vapour pressure. When the phosphorus vapour pressure is higher than 4 atm., almost 100% black ZnP_2 is formed.
The intermediate product is observed with short-time syhthesis method, and is identified by weight method, chemical analysis and SEM. We have proposed the main mechanism of ZnP_2 synthetic process. During the synthesis of ZnP_2 in a evacuated quartz tube, the ZnP_2 shell can be formed at the surface of the melted Zn. Then the synthetic rate of ZnP_2 mainly depend on volatilizing extent of Zn_3P_2 and ZnP_2 in the shell at high temperature. This mechanism can explaine the fact that the synthesis of ZnP_2 requires sufficient time and that the temperature control at the zinc end has an obvious effect on synthetic rate.