Phase Behavior of Rare Earth Manganites

作     者：NaokiKamegashira HiromiNakano GangChen JianMeng 

作者机构：DepartmentofMaterialsScienceToyohashiUniversityofTechnologyTempaku-choToyohashi441-8580Japan ElectronMicroscopeLaboratoryRyukokuUniversitySetaOtsu520-2194Japan DepartmentofAppliedChemistrySchoolofScienceHarbinInstituteofTechnologyHarbin150001China KeyLaboratoryofRareEarthChemistryandPhysicsChangchunInstituteofAppliedChemistryChineseAcademyofSciencesChangchun130022China 

出 版 物：《Journal of Rare Earths》 (稀土学报（英文版）)

年 卷 期：2004年第22卷第5期

页      面：582-585页

核心收录：

学科分类：0709[理学-地质学] 0819[工学-矿业工程] 081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 0708[理学-地球物理学] 0703[理学-化学] 070301[理学-无机化学] 

基　　金：ProjectsupportedbytheGrant in AidforScientificResearch (B13 45 0 2 5 9)bytheJapanSocietyforthePromotionofScienceandNSFC ( 2 0 3 3 10 3 0 2 0 2 710 49) 

主　　题：phase behavior layered perovskite pyrochlore-related structure rare earth manganese oxide 

摘      要：Among complex oxides containing rare earth and manganese BaLn_2Mn_2O_7 (Ln=rare earth) with the layered perovskite type and Ln_2(Mn, M)O_7 with pyrochlore-related structure were studied since these compounds show many kinds of phases and unique phase transitions. In BaLn_2Mn_2O_7 there appear many phases, depending on the synthetic conditions for each rare earth. The tetragonal phase of so-called Ruddlesden-Popper type is the fundamental structure and many kinds of deformed modification of this structure are obtained. For BaEu_2Mn_2O_7 at least five phases have been identified from the results of X-ray diffraction analysis with the space group P4_2/mnm, Fmmm, Immm and A2/m in addition to the fundamental tetragonal I4/mmm phase. In the pyrochlore-related type compounds, Ln_2Mn_(2-x)M_xO_7 (M=Ta, Nb, W etc), there also appear several phases with different crystal structures. With regard to every rare earth, Ln_2MnTaO_7 phase is stable only for excess Ta and can be obtained under high oxygen partial pressure process. This group has trigonal structure with zirkelite type (P3_121 space group). On the other hand Ln_2Mn_(2/3)Nb_(4/3)O_7 phase has monoclinic (C2/c space group) and zirconolite type structure. All of these structural models have the fundamental structure based on HTB (hexagonal tungsten bronze) layers formed by the arrangement of oxygen octahedra.