Rietveld全谱拟合定量分析Mn1.28Fe0.67P0.48Si0.55磁热材料相变前后的物相表征

Quantitative Analysis of Phase Characterization of Mn1.28Fe0.67P0.48Si0.55 Compound by Rietveld Refinement of XRD Whole-Patterns

以Mn1.28Fe0.67P0.48Si0.55为例,在氩气保护下通过高能球磨机械合金化和固相粉末烧结法合成样品,先使用振动样品磁强计VersaLab测出其居里温度为250K,在相变(发生铁磁-顺磁转变)温度附近选取220,240,250,260,270,280,300K温度点,利用变温XRD粉末衍射技术对其物相结构进行测量,得到不同温度下的XRD图谱。通过HighScore Plus软件结合数据库对物相定性拟合,再利用FullProf软件进行Rietveld拟合精修。精修结果表明,相变前后样品的晶体结构不发生变化,但随着温度的升高,晶格常数c呈现逐渐上升的趋势,而晶格常数a则呈现逐渐下降的趋势,同时主峰(211)向高角度发生偏移,证实了晶格常数的改变会导致峰形偏移的理论。此外化合物在不同温度下均为三相并存(两个Fe2P型六角结构相和一个(Fe,Mn)3Si相),并拟合出三相占比。精修后样品的修正因子Rwp值均小于15%,gof值小于5。

To analyze the phase characterization of Mn1.28Fe0.67P0.48Si0.55,the samples were prepared by using high-energy ball milling mechanical alloying and solid-state sintering of powder.According its Curie temperature of 250K determined by Versa Lab magnetometer,different temperatures above or below 250K,like 220,240,250,260,270,280,300K,were set to obtain the X-ray diffraction patterns respectively by analyzing the phase structure using X-ray powder diffraction technique under variable temperature.The phases were identified by High Score plus software and then the structure Rietveld refinement of the spectra at different temperatures was carried out by Full Prof software.The results showed that the crystal structures of the samples kept no change before and after the phase transition,but the lattice constant c increased and lattice constant a decreased with the increase of temperature,meanwhile,the main peak(211)shifted to a high angle,confirming the theory that the change of lattice constant led to the shift of diffraction peak.The research also found that because of the transition from the ferromagnetic to the paramagnetic,the compound was three phase co-existing at different temperatures near Curie point in some proportion,including two Fe2P phases and one(Fe,Mn)3Si phase.Quantitative analysis indicated that the Rwp value was less than 15%and the gof value was less than 5,suggesting that the experimental data of sample was reliable.