Synthesis of cubic Cs2FeSi5O12 powder in Ar atmosphere and its thermal expansion property

Cubic Cs2FeSi5O12 powder with the space group Ia-3d was synthesized by heat ing the powder mixture of Cs2CO3. 2H(2)O, Fe3O4 and amorphous SiO2 with the molar ratio of Cs/Fe = 2 and Si/Fe = 5 at 1273 K for 20 h under Ar gas flo w. The thermal expansion property of cubic Cs2FeSi5O12 powder was investiga ted in the temperature range from 298 to 1273 K using high-temperature X-ra y diffraction. The thermal expansion rate of cubic Cs2FeSi5O12 was lower th an that of cubic CsFeSi2O6. Consequently, increasing the molar ratio of Si/ Fe was effective for decreasing the thermal expansion rate of Cs-Fe-leucite compounds. Cubic Cs2FeSi5O12 showed a lower thermal expansion with the mea n linear thermal expansion coefficient of 1.75 x 10(-6) K-1 in the range fr om 573 to 1273 K.