2015年7月8日 星期三

用OriginPro8求XRD pattern 的半高寬(FWHM)


1.     先用OriginPro8打開XRD pattern



2.     點選Analysis > Fitting > Fit Single Peak,進入NLFit視窗




P.S 如果已經有使用過此功能,Fit Single Peak之後要點選Open Dialog 才能進入NLFit視窗

3.     進入NLFit視窗後,點選Setting > Data Selection


4.     點選Range1  然後點選Select Range from Graph



5.     完成上述步驟後,圖形兩端會出現游標



6.     把游標移至要測peak的底部兩端


7.     游標移至完成後,按Select data in graph視窗右邊的圖示


回到NLFit視窗,點選Fit


8.     會跳出Reminder Message視窗,點選Yes,在按OK


9.     之後會出現一個table, 表格上就會顯示你選擇的peak的半高寬(FWHM)




10.接著再帶入Scherrer equation計算particle size  (注意半高寬β要轉成弧度,即FWHM X π/180 = β)



where: 
τ is the mean size of the ordered (crystalline) domains, which may be smaller or equal to the grain size;
K is a dimensionless shape factor, with a value close to unity. The shape factor has a typical value of about 0.9, but varies with the actual shape of the crystallite;
λ is the X-ray wavelength;
β is the line broadening at half the maximum intensity (FWHM), after subtracting the instrumental line broadening, in radians. This quantity is also sometimes denoted as Δ(2θ);
θ is the Bragg angle.