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Study on Formation Condition and Cation Site Occupancy in Garnets

石榴石形成条件及阳离子位点占据研究

基本信息

批准号：
63460052
负责人：
OKADA Kiyoshi
金额：
$ 4.03万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

项目摘要

1. Natural garnetsSite occupancies in three kinds of Fe including garnets, i. e., pyrope(Py), andradite(An) and almandine(Al), have been investigated by EXAFS spectroscopy, single crystal X-ray diffraction (XRD) and analytical TEM methods. The R factors obtained by XRD structural refinement were under 2% for Py and Al but 4.8% for An. Site occupancies for Py, An and Al are as follows ;Py : (Fe^2+_. _<73>Ca_0. _<61>Mn_0. _<10>Mg_2. _<69>)(Al_3. _<98>Fe^3+_. _<03>)(Si_5. _<49>Al_0. _<58>)O_<24>,An : (Fe^2+_. _<83>Ca_5. _<06>Mn_0. _<20>)(Al_1. _<94>Fe^3+_. _<91>)(Si_5. _<99>Al_0. _<07>)O_<24>,Al : (Fe^2+_. _<87>Ca_0. _<13>Mn_0. _<19>Mg_0. _<91>)(Al_3. _<94>Fe^3+_. _<03>)(Si_5. _<93>Al_0. _<06>)O_<24>.Local structure around Fe ion has been examined by EXAFS using absorption spectra in the vicinity of K absorption edge. Interatomic distances of Fe-O in Py, An and Al were 2.26, 2.03 and 2.29A, respectively. Since the ionic dadii of Mg and Fe^<2+> are almost same, those obtained from XRD in Py and Al showed no significant difference. On the other hand, some difference in Fe-O distance can be detected by EXAFS because there is a difference in the ratio of Fe ion in 8 and 6 coordination sites for Py and Al. In this way, examination by both EXAFS and XRD was found to be very effective.2. Synthetic rare earth garnetsRecently various kinds of garnets have been synthesized. Formation of facet is usually reported in the Czechralski crystal growth. The slight difference of crystals between facet and off facet regions is considered to yield cracking in the crystals. It was clarified from the precise structure refinemnt by XRD that there is little difference in chemical composition but a small difference in interatomic distances.

1.天然石榴石矿赋存于三种铁矿物中，其中石榴石、铁尖晶石、铁尖晶石和铁尖晶石。例如，用EXAFS谱、X射线单晶衍射（XRD）和分析透射电镜（TEM）等方法研究了镁铝榴石（Py）、钙铁榴石（An）和铁铝榴石（Al）。通过XRD结构精修得到的R因子对于Py和Al小于2%，而对于An为4.8%。Py、An和Al的占位关系如下：Py：（Fe^2+_. _<73>Ca_0。_<61>Mn_0。- <10>Mg_2。_<69>）（Al_3. Fe^3<98>+。_<03>）（Si_5. _<49>Al_0. O<58>_<24>，An：（Fe^2+_. Ca<83>_5。_<06>Mn_0。_<20>）（Al_1. Fe^3<94>+。_<91>）（Si_5. _<99>Al_0. <07>Al<24>：（Fe^2+. _<87>Ca_0。_<13>Mn_0。_<19>Mg_0。_<91>）（Al_3. Fe^3<94>+。_<03>）（Si_5. _<93>Al_0.用<06><24>EXAFS研究了Fe ~（2+）O ~（2+）的局域结构。在Py、An和Al中，Fe-O原子间距分别为2.26、2.03和2.29。由于Mg和Fe^（2+）的离子半径几乎相同，因此Py和Al的XRD结果没有显著差异。另一方面，由于Py和Al的8位和6位配位Fe离子的比例不同，EXAFS可以检测到Fe-O距离的差异，因此EXAFS和XRD检测都是非常有效的.合成稀土石榴石近年来合成了各种各样的石榴石。在切氏晶体生长过程中，经常会出现小面的形成。小平面和离小平面区域之间的晶体的微小差异被认为在晶体中产生裂纹。通过X射线衍射（XRD）对结构的精细化分析表明，它们的化学组成差别不大，但原子间距差别不大。