研究目的
To understand the influence of thermal treatment on the relaxor characteristics and demonstrate quenching-induced stabilization of ferroelectric order in NBT-BT compositions.
研究成果
Quenching has been demonstrated to stabilize a ferroelectric order in the relaxor NBT-BT compositions, with the composition exhibiting higher tetragonality undergoing a spontaneous relaxor to ferroelectric transition. The reversibility of this effect upon annealing in oxygen atmosphere suggests the role of the quenching-induced increase in the defect concentration that favors a ferroelectric order in this system.
研究不足
The study focuses on two specific compositions of NBT-BT, and the findings may not be generalizable to other compositions or materials. Further investigation is necessary to ascertain the role of defect order/disorder and the influence of oxygen vacancies on the structure and the local polar regions.
1：Experimental Design and Method Selection:
The study investigated the quenching effect on two non-ergodic relaxor compositions at the morphotropic phase boundary (MPB), viz., NBT with 6 and 9 mol.% BT. The aim was to understand the influence of thermal treatment on the relaxor characteristics and demonstrate quenching-induced stabilization of ferroelectric order.
2：Sample Selection and Data Sources:
Stoichiometric amounts of Bi2O3, BaCO3, Na2CO3, and TiO2 were milled, calcined, remilled, compacted, and sintered. Samples were either furnace cooled or quenched from 1100°C.
3：List of Experimental Equipment and Materials:
Planetary ball mill, x-ray diffraction (Bruker D8), impedance analyzer (Alpha-Analyzer, Novocontrol), laser vibrometer (Polytec VDD-E-600 and a Polytec OFV-505 sensor head), Sawyer-Tower circuit, optical displacement sensor.
4：Experimental Procedures and Operational Workflow:
Electrical characterization was performed on electroded samples using silver paste. Temperature-dependent permittivity, in-situ d33, and polarization- and strain-hysteresis were measured.
5：Data Analysis Methods:
Lattice parameters were evaluated from LeBail fits of the diffraction data. Temperature and frequency-dependent permittivity measurements were analyzed to observe relaxor-ferroelectric transitions.
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