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

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.新型K_2NiF_4结构稀土锰氧化物的研究BaLnMnO_4（Ln = Nd，La）单晶在还原气氛中退火得到新相。结构变化是由氧缺乏引起的，并且通过在还原性气氛中退火形成少量Mn^<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人们合成了许多新相，并对其结构、电学性质、热学性质和磁学性质进行了研究。对于（A^<0.67>Ln^<0.33>）（Mn^<0.33>Ti^<0.67>）O_3（Ln=稀土，A=Ca，Sr），其电导率与结构参数（Mn-O角、Mn-O距离、离子半径、t因子和库仑电位）密切相关.高温下相态的原位观察用高温TEM和XRD研究了层状钙钛矿结构BaLn_2Mn_2O_7的一级相变。结构变化是由结构变形和电气结构变化引起的。通过高温TEM进行原位观察是有效的，以便了解真实的结构变化。而ABO_3型钙钛矿结构的样品则出现了二级相变。相变是由BO_6八面体的倾斜引起的。

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.