Structural phase transition, narrow band gap, and room-temperature ferromagnetism in [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} ferroelectrics

Journal Article · Mon Sep 15 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4896317· OSTI ID:22303504

Zhou, Wenliang; Yang, Pingxiong; Chu, Junhao ^[1]; Deng, Hongmei ^[2]

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1. Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)
2. Instrumental Analysis and Research Center, Institute of Materials, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

Structural phase transition, narrow band gap (E{sub g}), and room-temperature ferromagnetism (RTFM) have been observed in the [KNbO{sub 3}]{sub 1−x}[BaNi{sub 1/2}Nb{sub 1/2}O{sub 3−δ}]{sub x} (KBNNO) ceramics. All the samples have single phase perovskite structure, but exhibit a gradual transition behaviour from the orthorhombic to a cubic structure with the increase of x. Raman spectroscopy analysis not only corroborates this doping-induced change in normal structure but also shows the local crystal symmetry for x ≥ 0.1 compositions to deviate from the idealized cubic perovskite structure. A possible mechanism for the observed specific changes in lattice structure is discussed. Moreover, it is noted that KBNNO with compositions x = 0.1–0.3 have quite narrow E{sub g} of below 1.5 eV, much smaller than the 3.2 eV band gap of parent KNbO{sub 3} (KNO), which is due to the increasing Ni 3d electronic states within the gap of KNO. Furthermore, the KBNNO materials present RTFM near a tetragonal to cubic phase boundary. With increasing x from 0 to 0.3, the magnetism of the samples develops from diamagnetism to ferromagnetism and paramagnetism, originating from the ferromagnetic–antiferromagnetic competition. These results are helpful in the deeper understanding of phase transitions, band gap tunability, and magnetism variations in perovskite oxides and show the potential role, such materials can play, in perovskite solar cells and multiferroic applications.

• OSTI ID: 22303504
• Journal Information: Applied Physics Letters, Vol. 105, Issue 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETISM
BARIUM COMPOUNDS
CERAMICS
CRYSTALS
DIAMAGNETISM
FERROELECTRIC MATERIALS
FERROMAGNETISM
NICKEL COMPOUNDS
NIOBATES
ORTHORHOMBIC LATTICES
OXIDES
PARAMAGNETISM
PEROVSKITE
PHASE TRANSFORMATIONS
POTASSIUM COMPOUNDS
RAMAN SPECTROSCOPY
SOLAR CELLS
SYMMETRY
TEMPERATURE RANGE 0273-0400 K