High-Pressure Stabilization of New Transition Metal Oxides with the Perovskite Structure and Their Physical Properties

新型钙钛矿结构过渡金属氧化物的高压稳定及其物理性能

• 批准号: 09640680
• 负责人: SYONO Yasuhiko
• 金额: $ 1.54万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640680/
• 关键词: High-pressure synthesis; BiMnO_3; Ferromagnetism; Crystal structure analysis; Neutron diffraction; Tl-based cuprates; Superconductivity; 超伝導; BiMnO_3; 孤立電子対; ヤーンテラー歪; 衝撃圧縮; 酸化物; ペロブスカイト; 誘電体

High pressure synthesis has been utilized to stabilize new transition metal oxides with the perovskite structure, thereby achieving interesting physical properties like ferromagnetism and superconductivity. A ferro-magnet BiMnO_3 with T_cof 105K was synthesized at 4 GPa and 600ﾟC.Sr substitution for Bi reduces electrical resistivity considerably, but no metallic states were realized, unlike metallic, ferromagnet (La, Sr)MnO_3. Magnetic moment rather decreased with increasing Sr concentration and ferromagnetism completely disappeared around 40% Sr concentration.Crystal structure of monoclinically distorted perovskite was determined by neutron diffraction. Structure refinement using Rietveld analysis of powder pattern revealed that the Bi atom deviated remarkably from regular 12-coordinated sites owing to polarized 6s2 lone pair of Bi^<3+> ions. Every Mn^<3+> ions showed Jahn-Teller distortion. Superexchange interaction between adjacent Mn^<3+> ions were expected to be parallel for 2/3 and anti-parallel for 1/3, hence ferromagnetic interactions were considered to be dominated. Unlike LaMnO_3, rather homogeneous distribution of vacant dx_<2-y2> orbitals would explain the ferromagnetism of BiMnO_3.High pressure synthesis of TI-based cuprates was carried out for 1 .5-2.5GPa and around 1000ﾟC.New high Tc oxides of TlSr_2Ca_2Cu_3O_y and TlSr_2Ca_3Cu4O_<yp> wiht T_c of 97K and 90K were obtained. High pressure condition was considered to be favorable for preventing TI evaporation in long time annealing which was necessary for establishing ordered arrangement of Ca and Sr.Shock synthesis of high Tc cuprates was also tried. Tetragonal EuBa_2Cu_2O_<6.5> with cla= 3.0 was successfully synthesized by shock loading of the component mixture, but no superconductivity was realized by oxygen treatment. Superconductivity appeared only after annealing the as-shock-synthesized product above 900ﾟC, which established perfect order among Eu and Ba.

高压合成被用来稳定具有钙钛矿结构的新型过渡金属氧化物，从而获得铁磁性和超导电性等有趣的物理性质。在4 Gpa和600ﾟ的压力下合成了T_c值为105K的铁磁材料BiMnO_3。与金属铁磁材料(La，Sr)MnO_3不同的是，锶替代铋显著降低了材料的电阻率，但没有形成金属态。磁矩随锶含量的增加而减小，铁磁性在锶含量为40%左右完全消失。用Rietveld粉末图谱分析对结构进行了精细化，结果表明，由于6s2孤离子的极化，铋原子明显偏离了规则的12配位位置。所有的Mn^&lt；3+&gt；离子都表现出Jahn-Teller扭曲。相邻的Mn~(2+)和Lt~(3+)与Gt~(3+)离子之间的超交换相互作用预计为平行的2/3和反平行的1/3，因此认为铁磁相互作用占主导地位。与LaMnO_3不同的是，空位dx&lt；2-y2&gt；轨道的均匀分布解释了BiMnO_3的铁磁性。在1.5-2.5 Gpa和1000ﾟC左右的高压合成条件下，获得了TlSr2Ca2Cu3Oy和TlSr2Ca3Cu4O&lt；yp&gt；Yp&gt；TlSr2Ca2Cu3Cu4O&lt；Yp&gt；Yp&gt；T1Sr2Ca2Cu3Cu4O&lt；Yp&gt；T1Sr2Ca2Cu3Cu4Oy和TlSr2Ca3Cu4O&lt；yp&gt；Yp&gt；认为高压条件有利于在长时间的退火过程中防止钛的蒸发，这是建立钙和锶有序排列所必需的。还尝试了高T_c铜酸盐的休克法合成。用组分混合物冲击加载的方法成功合成了CLA=3.0的四方相EuBa2Cu2Olt；6.5&gt；，但氧气处理没有实现超导。冲击合成的产物在900ﾟC以上退火后才出现超导电性，这建立了Eu和Ba之间的完美秩序。

项目成果

K.Kusaba, Y.Shono and T.Kikegawa: "Phase transition of ZnO under high pressure and high temperature" Proc.Japan Acad.(in press.).

K.Kusaba、Y.Shono 和 T.Kikekawa：“高压高温下 ZnO 的相变”Proc.Japan Acad.（出版中）。

T.Atou et al.: "Structure determination of ferromagnetic perovskite BiMnO_3" submitted to J.Solid State Chem.

T.Atou 等人：“铁磁钙钛矿 BiMnO_3 的结构测定”提交给 J.Solid State Chem。

Y.Syono, H.Chiba and T.Atou: "Ferromagnetism in the (Bi, Sr) MnO_3 solid solution synthesized under high pressure" J.Mag.Soc.Jpn.22, Suppl., S1. 52-54 (1998)

Y.Syono、H.Chiba 和 T.Atou：“高压下合成的 (Bi, Sr) MnO_3 固溶体中的铁磁性”J.Mag.Soc.Jpn.22，增刊，S1。

T.Atou, H.Chiba, K.Ohyama, Y.Yamaguchi and Y.Shono: "Structure determination of ferromagnetic perovskite BiMnO_3" J.Solid State Chem. (submitted).

T.Atou、H.Chiba、K.Ohyama、Y.Yamaguchi 和 Y.Shono：“铁磁性钙钛矿 BiMnO_3 的结构测定”J.Solid State Chem。

T.Atou et al.: "Pressure effect on synthesis of TlSr_2Ca_2Cu_3O_y and TlSr_2Ca_3Cu O_y" Rev.High pressure Sci. & Tech.7. 1046-1048 (1998)

T.Atou 等人：“压力对 TlSr_2Ca_2Cu_3O_y 和 TlSr_2Ca_3Cu O_y 合成的影响”Rev.高压科学。