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Atomic scale investigation of enhanced ferroelectricity in (Ba,Ca)TiO3

机译:(Ba,Ca)TiO 3 中增强铁电的原子尺度研究

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The precise atomic positions and occupancies in (Ba,Ca)TiO3 ceramics have been characterized by high angle annular dark field (HADDF)-scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and annular bright field (ABF)-STEM. EELS precisely determines the distribution of Ba, Ca, and Ti ions in the perovskite structure, confirming the occupancy of ~7% Ca content at B-site in (Ba0.75Ca0.25)TiO3, which is the first direct evidence of Ca occupancy at the B-site in (Ba,Ca)TiO3 ceramics. ABF-STEM mapped the displacement of Ti ions and oxygen ions with respect to the center of Ba ions. By averaging the displacements of Ti and O ions in multiple single domains, it confirms the average Ti displacement of 0.263 ?, and large apical and equatorial oxygen displacement of 0.264 ? and 0.347 ?, respectively. Such great displacements in (Ba,Ca)TiO3 compared to BaTiO3 are direct evidence for the structure origin of the ferroelectric enhancement in Ca substituted BaTiO3.
机译:(Ba,Ca)TiO 3 陶瓷的精确原子位置和占有率已通过高角度环形暗场(HADDF)-扫描透射电子显微镜(STEM)进行了表征,电子能量损失谱(EELS)和环形明场(ABF)-STEM。 EELS精确地确定了钙钛矿结构中Ba,Ca和Ti离子的分布,从而证实了(Ba 0.75 Ca 0.25 )TiO 3 ,这是(Ba)B位置Ca占有率的第一个直接证据。 ,Ca)TiO 3 陶瓷。 ABF-STEM绘制了Ti离子和氧离子相对于Ba离子中心的位移。通过对多个单个畴中Ti和O离子的位移求平均值,可以确定平均Ti位移为0.263?,大的顶和赤道氧位移为0.264?。和0.347Ω。与BaTiO 3 相比,(Ba,Ca)TiO 3 的大位移是结构起源的直接证据。 Ca取代的BaTiO 3 中铁电增强的机理

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