高压下Fe_(92.5)O_(2.2)S_(5.3)的熔化温度

Melting Temperatures of Fe_(92.5)O_(2.2)S_(5.3) under High Pressure

采用反向碰撞法与光分析技术,测量了Fe_(92.5)O_(2.2)S_(5.3)(质量分数比)在208GPa下的声速,发现固态Fe_(92.5)O_(2.2)S_(5.3)的纵波声速在144GPa下开始减小,直到165GPa完全转变为液态体波声速,表明样品的完全熔化温度为(3 500±400)K。将该熔化温度作为参考点,应用Lindeman定律并外推至地球内外核边界可知,Fe_(92.5)O_(2.2)S_(5.3)的熔化温度为(5 000±400)K。通过比较Fe、Fe-O、Fe-S以及Fe-O-S的熔化温度,发现O元素对Fe熔化温度的影响很小,S元素对Fe熔化温度的降低与其含量成正比。如果外地核中S的质量分数为2%~6%,则地球内外核界面温度为5 000~5 400K。

In the present work we determined the sound velocities of shocked Fe92.5 O2.2S5.3 （in weight percent） under pressures up to 208 GPa using the reverse-impact method and the optical analyzer technique. We found that the longitudinal sound velocities of the solid Fe92.5 O2.2 S5.3 began to decrease at 144 GPa and completely transformed to bulk sound velocity of liquid at 165 GPa,indicating that the completely melting temperature of the sample is about （3 500±400）K based on the energy conservation relation. With respect to this point as reference, the melting temperature of Fe92.5O2.2S5.3 is about （5 000±400）K when extrapolated to the boundary of the inner/outer core using the Lindeman Law. Compared with the already measured melting temperatures of Fe, Fe-O, Fe-S and Fe-O-S, it shows that the oxygen has little effect on the melting of iron, and the melting depression of iron increases with sulfur content in the sample. If the mass fraction of the sulfur in the outer core is 2%-6%, the temperature is about 5 000-5 400 K at the inner core/outer core boundary of the Earth.