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Structure, dielectric properties of low-temperature-sintering BaTiO <sub/>3</sub> -based glass–ceramics for energy storage
摘要： The 0.85BaTiO3–0.15Bi(Mg2/3Nb1/3)O3 (BTBMN) ceramics with low-melting-temperature B2O3–Na2B4O7–Na2SiO3 (BNN) glass addition were prepared by the solid state method. The composition of the glass–ceramics was BTBMN–x wt.% BNN (x = 0, 1, 3, 5, 7, 9, 12, 15; abbreviated as BG). The sintering characteristics, phase structure, microstructure, dielectric properties and energy storage properties were systematically investigated. The sintering temperature of BTBMN ceramics was greatly reduced by the addition of BNN glass. The second-phase BaTi(BO3)2 was observed in the BG system until the glass content reached 15 wt.%. The addition of BNN glass significantly reduces the grain size of BTBMN ceramics. With the increase of BNN glass content, dielectric constant of BG glass–ceramics at 1 kHz gradually decreased, the maximum dielectric constant (εm) of BG glass–ceramics gradually decreased, while the temperature corresponding to the maximum dielectric constant (Tm) increased, the ferroelectric relaxation behavior decreased and the temperature stability of the dielectric constant gradually improved. As the BNN glass content increased, the breakdown electric field strength (BDS) of BG glass–ceramics increased first and then decreased, and the polarization values reduced gradually, while the trend of energy storage performance is similar to BDS. When the BNN glass content was 3 wt.%, the energy storage properties of the BG glass–ceramics were optimal, and a recoverable energy storage density (Wrec) of 1.26 J/cm3 and an energy storage efficiency (η) of 80.9% were obtained at the electric field strength of 220 kV/cm. The results showed that BG glass–ceramics were promising for energy storage capacitors.
关键词： Lead-free,glass–ceramics,relaxation,energy storage properties,BaTiO3
更新于2025-09-04 15:30:14
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Bright Orange Electroluminescence from Lead-Free Two-Dimensional Perovskites
摘要： Lead halide perovskites are important materials for solar cells and light emitting diodes (LEDs), but the toxicity of lead is a matter of concern for these and other commercial applications. Here, we demonstrate a lead-free two-dimensional (2D) Ruddlesden-Popper-type (C18H35NH3)2SnBr4 perovskite with a strong emission from the self-trapped states, whose photoluminescence quantum yields in colloidal suspension and in film are 88% and 68%, respectively. The insulating character of the organic oleylamine cation prevents electronic band formation between the [SnBr6]4- octahedron layers, which results in the Stokes-shifted orange emission. Electroluminescence of these 2D lead-free perovskite materials was demonstrated in an inverted LED structure with a low turn-on voltage of 2.2 V and a luminance of 350 cd/m2.
关键词： orange emission,two-dimensional perovskites,self-trapped states,lead-free,electroluminescence
更新于2025-09-04 15:30:14
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Enhanced Temperature Stability and Defect Mechanism of BNT-Based Lead-Free Piezoceramics Investigated by a Quenching Process
摘要： Because of the environmental concerns of eliminating lead from piezoelectric products, bismuth-based perovskite is becoming one of the most potential candidates. However, its relatively low thermal depolarization temperature (Td) is still an imperative obstacle hindering implementation of this material for practical application. Here, an enhanced temperature stability of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNTBT6) piezoceramics is reported, which can be obtained by the effective quenching process. Quenching process enhances the depolarization temperature to 136 °C, which is 40 °C higher than that of normal sintered samples. By using X-ray photoelectron spectroscopy and electron paramagnetic resonance methods, it is revealed that oxygen vacancy may exist in the quenched samples and consequently pins the domain walls, resulting in significant enhancement of depolarization temperature. Temperature-dependent dielectric, piezoelectric, and ferroelectric behaviors are measured as criteria to evidence the enhanced temperature stability.
关键词： lead-free BNT,quenching,defect mechanism,depolarization temperature
更新于2025-09-04 15:30:14
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Ionic conductive and dielectric properties of samarium isovalent doping in non-stoichiometric bismuth sodium titanate perovskite
摘要： Oxide ion-conducting solid electrolytes are of considerable importance as fuel cell component. Recently, Bi0.5Na0.5TiO3 (BNT)-based perovskite-structured oxides become a new hotspot of solid electrolyte since it has potential in oxygen ion conduction. Considerable ionic conductivity is achieved in a Bi deficient or an acceptor doping composition. In this work, the role of Sm content without lone pair electrons substituted for isovalent Bi is studied on the electrical properties of non-stoichiometric (Bi0.45Ca0.04)Na0.5TiO2.965 (BCNT). In the solid solution range, a transformation from resistive BCNT to dominated oxide ionic conductive process is revealed despite no additional designed vacancies involved. Interestingly, employment of smaller Sm cations by doping favors the plateau formation of dielectric permittivity at higher frequencies. Lone pairs substitution conception and shrinkage of lattice parameters are proposed to be responsible for the anomalous dielectric relaxation.
关键词： Bismuth sodium titanate,Lead free,Oxide ion conductors,Dielectrics
更新于2025-09-04 15:30:14