РОССИЙСКАЯ АКАДЕМИЯ НАУК

УРАЛЬСКОЕ ОТДЕЛЕНИЕ

ИНСТИТУТ ХИМИИ TBEPДОГО ТЕЛА
   
| | | | |
| | | |
 05.01.2009   Карта сайта     Language По-русски По-английски
Новые материалы
Экология
Электротехника и обработка материалов
Медицина
Статистика публикаци


05.01.2009

Synthesis, structural, magnetic and transport properties of layered perovskite-related titanates, niobates and tantalates of the type AnBnO3n+2, AAk−1BkO3k+1 and AmBm−1O3m




Purchase the full-text article




F. LichtenbergCorresponding Author Contact Information, a, E-mail The Corresponding Author, A. Herrnbergera and K. Wiedenmanna






aExperimentalphysik VI, Center for Electronic Correlations and Magnetism (EKM), Institute of Physics, Augsburg University, D-86135 Augsburg, Germany






Available online 26 October 2008.






Abstract


This article represents a continuation of a paper on AnBnO3n+2 = ABOx compounds which was published in 2001 in this journal. This work reports also on oxides of the type AAk−1BkO3k+1 (Dion–Jacobson type phases) and hexagonal AmBm−1O3m. The title materials have in common a layered perovskite-related structure whose layers are formed by corner-shared BO6 octahedra. The three homologous series differ structurally in their orientation of the BO6 octahedra with respect to the c-axis. This can be considered as a result from cutting the cubic perovskite ABO3 structure along different directions followed by an insertion of additional oxygen, namely along the [100], [110] and [111] direction for AAk−1BkO3k+1, AnBnO3n+2 and AmBm−1O3m, respectively. The materials, with emphasis on electrical conductors, were prepared by floating zone melting and characterized by thermogravimetric analysis, X-ray powder diffraction and magnetic measurements. On crystals of five different compounds the resistivity was measured along the distinct crystallographic directions. Concerning AnBnO3n+2 this work is focussed on two topics. The first are materials with paramagnetic rare earth ions at the A site or transition metal ions such as Fe3+ at the B site. The second are non-stoichiometric compounds. Furthermore, we discuss issues like occupational order at the B site, the proximity of some materials to the pyrochlore structure, potential magnetic ordering, and a possible coupling between magnetic and dielectric properties. The oxides AAk−1BkO3k+1 gained attention during a study of the reduced Ba–(Ca,La)–Nb–O system which lead to conducting Dion–Jacobson type phases without alkali metals. Concerning hexagonal AmBm−1O3m the emphasis of this work are conducting niobates in the system Sr–Nb–O. The title materials have in common a quasi-2D (layered) structure and they are mainly known as insulators. In the case of electrical conductors, however, their transport properties cover a quasi-1D, quasi-2D and anisotropic 3D metallic behavior. Also temperature-driven metal-to-semiconductor transitions occur. A special feature of the quasi-1D metals of the type AnBnO3n+2 is their compositional, structural and electronic proximity to non-conducting (anti)ferroelectrics. We speculate that these quasi-1D metals may have the potential to create new (high-Tc) superconductors, especially when they are viewed from the perspective of the excitonic type of superconductivity. Referring to literature and results from this work, a comprehensive overview on the title oxides and their properties is presented.





Keywords: Titanates; Niobates; Tantalates; Perovskite-related crystal structures; Layered materials; Crystal growth; Floating zone melting; Low-dimensional conductors; Resistivity; Magnetic susceptibility; Magnetic ordering; Ferroelectrics; Antiferroelectrics; Superconductivity; Excitonic superconductivity





Article Outline



1. Introduction and overview

1.1. Preliminaries and general survey
1.2. AnBnO3n+2 = ABOx
1.3. Dion–Jacobson type phases AAk−1BkO3k+1
1.4. Hexagonal AmBm−1O3m

2. Experimental

2.1. Sample preparation
2.2. Powder X-ray diffraction
2.3. Magnetic measurements
2.4. Resistivity measurements

3. Results and discussion: sample preparation
4. Results and discussion: Dion–Jacobson phases AAk−1BkO3k+1 without alkali metals
5. Results and discussion: AnBnO3n+2 = ABOx

5.1. Structural properties

5.1.1. AnBnO3n+2 and pyrochlore
5.1.2. Non-stoichiometric compounds
5.1.3. Occupational order at the B site

5.2. Resistivity
5.3. Magnetic susceptibility

5.3.1. Data evaluation in the case of Curie–Weiss behavior
5.3.2. Results and discussion in the case of Curie–Weiss behavior
5.3.3. The n = 5 titanates LnTiO3.4 with Ln = La, Ce, Pr, Nd or Sm

5.4. Speculations about the potential for (high-Tc) superconductivity

5.4.1. View from the perspective of excitonic superconductivity

Electronic polarizability
Ionic (or lattice) polarizability
Dipolar polarizability
Interfacial polarizability

5.4.2. The system Na–W–O

6. Results and discussion: hexagonal AmBm−1O3m
7. Summary

7.1. AnBnO3n+2 = ABOx
7.2. Dion–Jacobson type phases A' Ak−1BkO3k+1 without alkali metals
7.3. Hexagonal AmBm−1O3m

Acknowledgements
Tables of powder XRD data of some compounds
References






















































Дизайн и программирование N-Studio 
А Б В Г Д Е Ё Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ъ Ы Ь Э Ю Я
  • Chen Wev .  honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

  • © 2004-2019 ИХТТ УрО РАН
    беременность, мода, красота, здоровье, диеты, женский журнал, здоровье детей, здоровье ребенка, красота и здоровье, жизнь и здоровье, секреты красоты, воспитание ребенка рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок медицина, клиники и больницы, болезни, врач, лечение, доктор, наркология, спид, вич, алкоголизм православные знакомства, православный сайт творчeства, православные рассказы, плохие мысли, православные психологи рождение ребенка,пол ребенка,воспитание ребенка,ребенок дошкольного возраста, дети дошкольного возраста,грудной ребенок,обучение ребенка,родить ребенка,загадки для детей,здоровье ребенка,зачатие ребенка,второй ребенок,определение пола ребенка,будущий ребенок