In-situ observation of the phase conditions of rare erath manganites controlled by structure and crystal structure and application of new properties

我们合成了新的稀土锰氧化物，分析了新的晶体结构和新的性质。具有K_2NiF_4结构的新型稀土锰氧化物的研究在还原气氛中对单晶(I_4/mm)进行热处理，得到了BaLnMnO_4(Ln=Nd，La)新相。这种结构变化是由于氧缺乏引起的，在还原气氛中热处理形成了少量的Mn~(2+)&Gt~(2+)离子。Na-氧化物具有Fmmm对称性的晶体结构，La-氧化物具有Cccm对称性。具有钙钛矿结构的新型氧化物的研究合成了许多新相，并对其结构、电学性能、热性能和磁性进行了研究。在(A^&lt；0.67&gt；Ln^&lt；0.33&gt；)(Mn^&lt；0.33&gt；Ti^&lt；0.67&gt；)O_3(Ln=稀土，A=Ca，Sr)的情况下，电导率与结构参数(Mn-O角、Mn-O距离、离子半径、t因子和库仑电势)密切相关。高温下相状态的原位观察我们用高温透射电子显微镜和X射线衍射仪发现了层状钙钛矿结构的BaN_2Mn_2O_7的一级相变。结构的变化是由结构的变形和电结构的变化引起的。利用高温透射电子显微镜进行原位观察是实时了解组织变化的有效手段。另一方面，具有ABO_3结构的钙钛矿结构发生了二级相变。相变是由八面体BO_6的倾斜引起的。

We synthesized new rare-earth manganites, and analyzed new crystal structures and new properties.1. Study of new rare earth manganites with K_2NiF_4 structureNew phase of BaLnMnO4 (Ln = Nd, La) was obtained by annealing the single crystal (I4/mmm) in a reducing atmosphere. The structural change was caused by an oxygen deficiency, and a small amount of Mn^<2+> ions was formed by annealing in a reducing atmosphere. Na-oxide has a crystal structure with Fmmm symmetry, and La-oxide has Cccm symmetry.2. Study of new oxides with perovskite related structuresMany new phases have been synthesized and investigated their structures, electrical properties, thermal properties and magnetic properties. In the case of (A^<0.67>Ln^<0.33>)(Mn^<0.33>Ti^<0.67>)O_3 (Ln=rare earth, A=Ca, Sr), the electrical conductivity was closely related with structural parameters (Mn-O angles, Mn-O distances, ionic radii, t-factors, and coulomb potentials).3. In-situ observations of phase conditions at elevated temperatureWe found a first-order phase transition in BaLn_2Mn_2O_7 with a layered perovskite structure using a high-temperature TEM and XRD. The structure change was caused by a distortion of structure and change in electrical structure. In-situ observation by a high-temperature TEM was effective in order to know the structural change at real time. On the other hand, secondary-order phase transition was observed in perovskites with ABO_3 structure. The phase transition was caused by tilting of octahedra BO_6.