Search

Understanding ferroelectric characteristic is crucial, especially for elucidating the existence of ferroelectric and its relationship with hysteresis in hybrid organic–inorganic perovskites. Our focus is to evaluate the ferroelectric properties of MAPbI3 perovskite films by suppressing the rotation of the MA+ ions through the substitution of TMA+ cations. Our findings indicate that both MAPbI3 and MA0.85TMA0.15PbI3 exhibit non-ferroelectric properties at room temperature, which persist even after external polarization treatment. Further analysis reveals that the hysteresis in J–V characteristics is associated with ion migration phenomena. The external polarization treatment aids in releasing electrons from defect states, enabling them to revert to their original lattice sites. As a result, devices subjected to polarization treatment exhibit reduced hysteresis and enhanced photovoltaic performance. [ABSTRACT FROM AUTHOR]

The energy loss (Eloss) caused by inefficient charge transfer and large energy level offset at the buried interface can easily restrict the performance of p-i-n perovskite solar cells (PVSCs). In this study, the utilization of poly-TPD and P3CT-N as a dual-hole transporting layer (HTLs) was implemented in a sequential manner. This approach aimed to improve the charge transfer efficiency of the HTL and mitigate charge recombination at the interface between the HTL and PVK. The results showed that this strategy also could achieve more suitable energy levels, improve the quality of the perovskite film layer, and ultimately enhance the device's stability. IPVSCs employing the dual-HTLs approach exhibited the highest power conversion efficiency of 19.85%, and the open-circuit voltage increased to 1.09 V from 1.00 V. This study offers a straightforward and efficient approach to boost the device performance by minimizing Eloss and reducing the buried interfacial defects. The findings underscore the potential of employing a dual-HTL strategy as a promising pathway for further advancements in PVSCs. [ABSTRACT FROM AUTHOR]

(1- x )Bi .49 Er .01 Na .5 TiO 3 - x K .5 Na .5 NbO 3 (abbreviated as BENT- x KNN) ceramics have been prepared via solid state reaction technique and their electric properties have been investigated by impedance spectroscopy. X-ray diffraction results show that the incorporation of KNN into BENT forms (Bi .49 Er .01 ) 1- x K .5 x Na .5 Ti 1- x Nb x O 3 solid solution with perovskite structure. Dielectric measurements reveal that there exists a diffuse anomaly above permittivity-maximum temperature whether heating or cooling, which exhibits thermal hysteresis at low frequency. It is proposed that the anomaly is probably ascribed to weakly bound electrons trapped in Nb Ti • and V O • • defects based on a piecewise fitting for their conductivity vs. temperature. [ABSTRACT FROM AUTHOR]

Reddish orange-emitting 0.8Bi 0.5 Na 0.5 TiO 3 -0.2SrTiO 3 - x Sm ferroelectric ceramics were prepared by the conventional solid-state reaction route, and their electrical and optical temperature stability were also investigated. Temperature-dependent measurement of polarization revealed that the addition of Sm 3+ ion significantly improved their thermal stability of ferroelectric properties. Temperature-dependent photoluminescent spectra showed that the 0.8Bi 0.5 Na 0.5 TiO 3 -0.2SrTiO 3 - x Sm multifunctional ceramics exhibit well thermal stability of photoluminescence in the temperature range from 20 °C to 160 °C, which is superior to the thermal stability of the KBaPO 4 :Sm phosphors. [ABSTRACT FROM AUTHOR]

Highlights: [•] BaTi0.8(Ni0.5Nb0.5)0.2O3 ceramics in the 100–300K region are a face-centered Fm m structure. [•] Its dielectric characteristics show a dielectric relaxation in the 175–250K region. [•] The low temperature relaxation is ascribed to the dipolar defect. [ABSTRACT FROM AUTHOR]

Abstract: Structural and dielectric properties of yMgO–(1− y)Ba0.60Sr0.40TiO3 (BST) (where y =3, 5, 10, 20, 30 and 40mol%) ceramics prepared by using sol–gel derived powders have been investigated. It is found that a careful control of the synthesis process enables producing a pure perovskite BST phase at a relatively low calcining temperature of 600°C. Two phases, corresponding to BST and MgO phases, are clearly visible when MgO content up to 20mol%. The influence of MgO additive on dielectric properties of BST ceramics can be classified into two categories: one is the substitution effect of Mg2+ ions and the other is the “composite” effect of MgO. [ABSTRACT FROM AUTHOR]

Abstract: Dielectric characteristics of BaTi1−x (Co0.5Nb0.5) x O3 (x=0.2, 0.4 and 0.6) ceramics are investigated together with mixed-valence structure. X-ray diffraction shows that all samples are cubic perovskite phase at room temperature. As the sintering temperature increases, grain size increases, accompanying obvious change in dielectric response. The samples with larger grains exhibit the giant dielectric characteristics, which are considered to be attributed to domain boundary effect. The frequency dependence of the loss peak is found to obey the Arrhenius law with an activation energy of ~0.3eV, which is assigned to be the result of charge ordering. [Copyright &y& Elsevier]

Understanding ferroelectric characteristic is crucial, especially for elucidating the existence of ferroelectric and its relationship with hysteresis in hybrid organic–inorganic perovskites. Our focus is to evaluate the ferroelectric properties of MAPbI3 perovskite films by suppressing the rotation of the MA+ ions through the substitution of TMA+ cations. Our findings indicate that both MAPbI3 and MA0.85TMA0.15PbI3 exhibit non-ferroelectric properties at room temperature, which persist even after external polarization treatment. Further analysis reveals that the hysteresis in J–V characteristics is associated with ion migration phenomena. The external polarization treatment aids in releasing electrons from defect states, enabling them to revert to their original lattice sites. As a result, devices subjected to polarization treatment exhibit reduced hysteresis and enhanced photovoltaic performance. [ABSTRACT FROM AUTHOR]

Abstract: A new lead-free perovskite system of BaTi1−x (Li2/3Nb2/3) x O3 (x =0.02, 0.05, 0.07 and 0.10) has been synthesized by the mixed-oxide route. Temperature and frequency dependences of permittivity show a crossover from ferroelectric to relaxor behavior. For the samples with x ≥0.05, the frequency-dependent T m satisfying the Vögel–Fulcher formula indicates a relaxor behavior. The increase with orders of magnitude in E a with respect to x is possibly ascribed to more Ba-vacancies. Remnant polarization and strain decrease with increasing x due to phase transformation from ferroelectric tetragonal to paraelectric pseudocubic at room temperature. [Copyright &y& Elsevier]

Abstract: BiFeO3 nanopowder has been prepared by the nitric acid-assisted gel process and its structure, optical and magnetic properties has been studied. XRD and FTIR results show that the BiFeO3 powder calcined at 550°C exhibits a rhombohedrally distorted perovskite structure without secondary phase. Meanwhile, the BiFeO3 powder has a bandgap of 2.19eV and exhibits the weak ferromagnetic nature at room temperature. [Copyright &y& Elsevier]

In this work, <001> oriented 0.90(Bi 0.5 Na 0.5 )TiO 3 –0.05KNbO 3 –0.05SrTiO 3 (BNT–KN–ST) ceramics with high degree of texturing were produced by templated grain growth using different perovskite plate-like (Bi 0.5 Na 0.5 )TiO 3 and SrTiO 3 as template particles. The effects of different template particles on the grain orientation, structure evolution, phase stability and strain response was systematically investigated to develop the lead-free piezoelectric materials with an excellent actuating performance. The strain response increased monotonously with the increase in the degree of texturing and the optimized microstructure was found to provide excellent strain properties with a large strain of 0.38% and normalized strain S max / E max = 540 pm/V for the textured samples with BNT template particles at room temperature as compared to the random counterparts. The temperature-dependent strain response is also compared to randomly oriented ceramics and the results demonstrated that the textured piezoceramics with BNT template particles exhibited the enhancement in the temperature stability over the temperature range room temperature-120 °C. [ABSTRACT FROM AUTHOR]