全谱拟合定量分析方法及其影响因素的研究

Study on the Effecting Factors of Quantitative Analysis by Rietveld Method

为研究全谱拟合定量分析方法,将此定量分析方法与内标法、K值法、绝热法进行对比分析,主要讨论了图谱的收集方式、拟合过程中所用的峰形函数,以及温度因子对全谱拟合定量分析结果的影响。结果表明,相对其他定量方法,全谱拟合定量分析只需知物相的结构信息,无需标样,具有较高的准确性。另外,衍射角的收集范围通常与被测试样材料有关,一般扫描范围包括待测试样的主要衍射峰区域即可;步长越小,每步扫描时间越长,衍射强度高,拟合因子越小,计算图谱与实测图谱吻合程度越好;基本参数法通过已知实验仪器的几何参数计算出仪器的仪器峰形,可简化精修过程,减少人为误差;选用结构数据库中的结构信息进行的拟合定量,得到的拟合因子最小,拟合结果最好;拟合过程中修正阳离子的温度因子比修正氧离子的温度因子得到的拟合因子小,拟合定量结果较好一些。

In order to study the quantitative analysis by the Rietveld method,the internal standard method,K value method and heat insulation method were analyzed.And the factors which affected the results of the Rietveld method had been studied,which included the collection range of pattern,the peak shape function and the temperature factor.The results indicated that the Rietveld method was more accurate than other quantitative methods.The structure information of crystal phase was only needed and the internal standard was not unnecessary for the Rietveld method.In addition,the collection range of pattern depended on the tested materials,and the scanning range should include the main diffraction peak of the sample.Smaller step size and longer scan time of each step made the fitting factor smaller,also the calculated pattern coincided with the measured pattern better.The fundamental parameter method could calculate the peak shape by geometric parameters of experimental instrument,which could simplify the refinement process and reduce artificial error.During the fitting process,the fitting factor which has obtained by refining the cationic temperature factor was smaller than that obtained by refining the temperature factor of oxygen ions,also the testing result was more accurate.And when using the structural information of database,the fitting factors were the minimum and the fitting results were the best.