Differential thermal/thermogravimetric analysis (DTA-TG) and thermal expansion anomaly properties of Tm2Fe17 compound

The structure, the magnetic and thermal expansion properties of Tm₂Fe₁₇ compound and its nitrides have been investigated by means of x-ray diffraction, magnetization measurements and Simultaneous Thermal Analyzer as well. The result shows that with the temperature increasing from 200 K to 1200 K under the protection of N₂, Tm₂Fe₁₇N_x compound is formed due to the diffusion of the interstitial N atoms. There appears a higher Curie temperature in Tm₂Fe₁₇N_x compound than its mother compound Tm₂Fe₁₇. At higher temperature than 650K, the nitrogenized reaction of Tm₂Fe₁₇ is sufficient, in the meantime, the decomposed reaction of Tm₂Fe₁₇N_x whose by-products include α - Fe takes place. The structure analysis indicates that Tm₂Fe₁₇N_x compound exhibits only single phase of Th₂Ni₁₇ below 1200K. The investigation of thermal expansion shows there exits an anisotropic negative thermal expansion in the temperature range from 300K to 340K, and the coefficient of the average thermal expansion is α̅ = -1.92×10^-5/K.