XRD measurement of mean thickness, thickness distribution and strain for illite and illite-smectite crystallites by the Bertaut-Warren-Averbach technique
XRD measurement of mean thickness, thickness distribution and strain for illite and illite-smectite crystallites by the Bertaut-Warren-Averbach technique
复制标题
DOI：
10.1346/ccmn.1998.0460105
复制
发表时间：
1998-02-01
影响因子：
2.2
通讯作者：
Srodon, J
中科院分区：
文献类型：
--
作者：
Drits, VA;Eberl, DD;Srodon, J
Bertaut-Warren-Averbach （BWA）技术的改进版本（Bertaut 1949, 1950; Warren and Averbach 1950）已经开发出来，通过分析x射线衍射（XRD）数据来测量矿物中的相干散射域（CSD）大小和应变。该方法用于测量伊利石和伊利石-蒙脱石（is）的计算和实验XRD谱图的CSD厚度分布。该方法几乎准确地恢复了计算出的伊利石XRD图的CSD厚度分布。天然I-S样品含有膨胀层，导致c*方向上的非周期性结构，并且由于混合层状导致XRD峰变宽和不对称。因此，这些峰不能用BWA方法分析。这些困难可以通过k饱和和x射线分析之前的加热来克服，以形成10埃的周期结构。BWA分析得出混合层晶体（基本伊利石粒子的相干衍射堆栈）的厚度分布。对于大多数IS样本，CSD厚度分布可以用对数正态函数近似。混合层晶体的平均厚度和可膨胀性可以用来计算伊利石颗粒的基本平均厚度。对脱水、饱和k样品的分析表明，对称应变使基底XRD反射变宽，这可能与脱水引起的蒙脱石夹层局部变化有关，应变的标准差随膨胀率有规律地增大。001和002反射仅受该应变的轻微影响，因此适用于CSD厚度分析。BWA法测得的脱水I-S混合层平均晶体厚度与积分峰宽法测得的晶体厚度非常接近。
A modified version of the Bertaut-Warren-Averbach (BWA) technique (Bertaut 1949, 1950; Warren and Averbach 1950) has been developed to measure coherent scattering domain (CSD) sizes and strains in minerals by analysis of X-ray diffraction (XRD) data. This method is used to measure CSD thickness distributions for calculated and experimental XRD patterns of illites and illite-smectites (IS). The method almost exactly recovers CSD thickness distributions for calculated illite XRD patterns. Natural I-S samples contain swelling layers that lead to nonperiodic structures in the c* direction and to XRD peaks that are broadened and made asymmetric by mixed layering. Therefore, these peaks cannot be analyzed by the BWA method. These difficulties are overcome by K-saturation and heating prior to X-ray analysis in order to form 10-Angstrom periodic structures. BWA analysis yields the thickness distribution of mixed-layer crystals (coherently diffracting stacks of fundamental illite particles). For most IS samples, CSD thickness distributions can be approximated by lognormal functions. Mixed-layer crystal mean thickness and expandability then can be used to calculate fundamental illite particle mean thickness. Analyses of the dehydrated, K-saturated samples indicate that basal XRD reflections are broadened by symmetrical strain that may be related to local variations in smectite interlayers caused by dehydration, and that the standard deviation of the strain increases regularly with expandability. The 001 and 002 reflections are affected only slightly by this strain and therefore are suited for CSD thickness analysis. Mean mixed-layer crystal thicknesses for dehydrated I-S measured by the BWA method are very close to those measured by an integral peak width method.