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The Sr1-xLaxTi1-xCrxO3 (x = 0–0.05) nanofibers were synthesized by electrospinning based on Pechini sol-gel method. The prepared Sr1-xLaxTi1-xCrxO3 nanofibers were analyzed by XRD, Raman, UV–vis spectra, XPS, SEM, TEM, transient photocurrent, electrochemical impedance and photocatalytic hydrogen evolution tests. The results showed that CrLa co-doped can expand the light absorption region of SrTiO3 from the ultraviolet region to the visible light, and significantly narrowed its band gap. Under visible light irradiation, Sr1-xLaxTi1-xCrxO3 nanofibers exhibited the best hydrogen evolution activity at x = 0.03, and the hydrogen evolution rate reached 106.2 μmol∙g−1∙h−1. This may be the result of the combined effect of the intermediate band gap and the band gap variation due to Cr doping.

Ti4+-ion-doped (n + 1)SrO − nCeO2 (n = 2) ceramic systems were prepared with the conventional solid-state reaction method, and the effects of the phase structures and compositions, sintering behaviors, microstructures and microwave dielectric properties of these ceramic systems were investigated in detail as a function of TiO2 content. The analytical results of the XRD patterns show that the pure (n + 1)SrO − nCeO2 (n = 2) system is a composite-phase ceramic system with coexisting SrCeO3 and Sr2CeO4 phases (represented as a SrCeO3 + Sr2CeO4 system), which belong to the orthogonal structures of the Pmcn (62) and Pbam (55) space groups, respectively. For the xTiO2-(1 − x) (SrCeO3 + Sr2CeO4) (x = 0.1–0.4) ceramic samples, the secondary phase Sr2TiO4 can also be detected within the range of the investigated components. Meanwhile, the Raman spectroscopy, SEM-EDS, and HRTEM (SAED) analysis results also verified the correctness and consistency of the phase structures and compositions for all the given specimens. In addition, complex impedance spectroscopy was used to detect the conductive behavior of these compound ceramic systems, and the calculation results show that the appropriate addition of Ti4+-ions can make the SrCeO3 + Sr2CeO4 system have better thermal stability. The composition of x = 0.2 multiphase structural ceramic sample sintered at 1330 °C for 4 h has a near zero τf value of ~−4.6 ppm/°C, a moderate εr of ~40.3 and a higher Q × f~44,020 GHz (at 6.56 GHz). The relatively superior-performing ceramics developed in this work are expected to provide a promising microwave dielectric material for communication components.

A sol–gel method is employed for preparing high quality lead-free glass-ceramic samples (1 − x)BCZT-xBBS—incorporating Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powder and Bi2O3-B2O3-SiO2 (BBS) glass-doped additives with different values of x (x = 0, 0.05, 0.1, 0.15). Systematic investigations are performed to comprehend the structural, dielectric and energy storage characteristics using X-ray diffraction, field-emission scanning electron microscopy, impedance and ferroelectric analyser methods. With appropriate BBS doping (x), many fundamental traits including breakdown strength, dielectric loss and energy storage density have shown significant improvements. Low doping-level samples x < 0.1 have retained the pure perovskite phase while a second glass phase appeared in samples with x ≥ 0.1. As the doping level (0.1 ≥ x > 0) is increased, the average grain size decreased to become better homogeneous materials with improved breakdown energy strengths. Excessive addition of BBS (x = 0.15) causes negative effects on microstructures and other traits. The glass-ceramic sample 0.95BCZT-0.05BBS exhibits excellent dielectric permittivity and temperature stability, with the highest energy storage density of 0.3907 J cm−3 at 130 kV cm−1. These results provide good reference to develop lead-free ceramics of high energy storage density.

Abstract The structure of the ferroelectrics has been widely studied in order to pursuing the origin of high electromechanical responses. However, some experiments on structure of ferroelectrics have yielded different results. Here, we report that the controversial phase structure is due to the adaptive diffraction of nanodomains which hides the natural crystal structure, and the electric-field-induced phase transition is that the natural crystal structure reappears due to the coalescent nanodomains or ordering nanodomains by applying a high electric field. The temperature dependence of dielectric constant with different measurement frequencies and X-ray diffraction (XRD) patterns of unpoled, poled, and annealing after poled ceramics in Bi0.5Na0.5TiO3–BaTiO3 (BNT–BT) ceramics authenticate the statement. These results provide a new insight into the origin of structural complexity in ferroelectric ceramics, which is related to the key role of nanodomains.

The effect of thermal and electrical histories on structure and dielectric behaviors is studied using 0.95(Bi0.5Na0.5)0.97(Li0.5Nd0.5)0.03TiO3-0.05BaTiO3 (abbreviated as BNTLN0.03-BT5) ceramic as a selected system. Subtle structure change caused by annealing treatment, and pronounced phase transition and domain switching by electrical poling, are observed to occur, respectively. The dielectric constant and its strong frequency dispersion in unpoled samples decrease evidently by electrical poling due to electric field-induced ordered domain. The high temperature Maxwell-Wagner relaxor behavior vanishes by annealing treatment due to the loss of electrical inhomogeneity with interface charging effects. Piezoelectric properties are improved evidently by annealing treatment at 900 °C, implying a new appropriate method to improve piezoelectric properties.

Abstract (Ba1−x Sr x )4(Sm0.4Nd0.6)28/3Ti18O54 (x = 0.02, 0.04, 0.06, 0.08, 0.1) solid solutions were prepared by the conventional solid-state reaction process. It was found that (Ba1−x Sr x )4(Sm0.4Nd0.6)28/3Ti18O54 ceramics are fully composed of BaSm2Ti4O12 and BaNd2Ti5O14 phases for all the compositions. The increasing x value (0.02 ≤ x ≤ 0.1) in ((Ba1−x Sr x )4(Sm0.4Nd0.6)28/3Ti18O54 ceramics can not only obtain high Q × f value but also effectively enhance the permittivity (ε r). The (Ba1−x Sr x )4(Sm0.4Nd0.6)28/3Ti18O54 ceramic with x = 0.08, sintered at 1440 °C for 4 h, shows excellent microwave dielectric properties of permittivity (ε r) ≈ 93.19, quality factor (Q × f) ≈ 9770.14 GHz (at 3.415 GHz), and almost near-zero temperature coefficient of resonant frequency (τ f ) ≈ +4.56 ppm/°C.

Microstructure and dielectric behaviors of heating/cooling and bias-field were investigated in lead-free ceramics (1−x)Bi0.5Na0.5TiO3−xBaTiO3 (BNT−xBT, x=0, 0.02, 0.04, 0.06, 0.08 and 0.10). The relaxor characters and the Vogel–Fulcher law of frequency-dependent dielectric properties were analyzed. Three dielectric anomalies with pronounced frequency dispersion at Td, a maximum dielectric with variable frequency-dispersion at Tm and a third Maxwell–Wagner-type relaxation over a wide temperature range in high-temperature region were observed. The significant dielectric thermal hysteresis, low barrier energy, high freezing temperature in heating process and the maximum dielectric tunability appeared in x=0.4 ceramic.

The (Bi0.5Na0.5)0.94Ba0.06Ti1-x (Nd0.5Ta0.5) xO3 (0.01≤x≤0.05) lead-free ceramics (BNBT-xNT) used (Nd0.5Ta0.5)4+ complex-ions to modify its structure and electrical properties. The BNBT-xNT ceramics exhibit the coexistence of tetragonal and rhombohedral phase. The (Nd0.5Ta0.5)4+ complex-ions prohibit grain growth, and its average grain size decreases from 2.53 µm to 0.84 µm with increasing complex-ion content. The NT doping not only induces the transformation from ferroelectric phase to relaxor ferroelectric phase but also decreases the coercive field and remnant polarization. The permittivity curves are broadened at heavily doping content. The energy storage and strain properties are improved by complex-ions. The maximum energy storage density of 0.475 J/cm3 is obtained at x = 0.035 and 60 kV/cm, the energy storage efficiency achieves the maximum efficiency of 61.5% at x=0.05. As increasing complex-ion content, the typical butterfly-shaped strain curve develops into a sprout-shaped one, and the maximum strain of 0.199% is obtained at x=0.02.

Lead-free (1–x)(0.4BiScO(3)–0.6BaTiO(3))-x(Bi(0.5)Na(0.5))TiO(3) (BSBT–xBNT) ceramics were prepared by traditional ceramics preparation method. The energy storage characteristics, as well as dielectric spectrum curves of BSBT–xBNT ceramics, were systematically used in research. The ternary system formed perovskite solid solution with dense and homogenous microstructure. BSBT–xBNT ceramics exhibited slimmer and slanted hysteresis loops followed by higher saturation polarisation (P(max)) and lower remnant polarisation (P(r)), which induced high-energy storage density of 1.39 J/cm^3 (E = 180 kV/cm). Ranging from 200 to 400°C, BSBT–xBNT ceramics had high permittivities, and a matching dielectric loss, which exhibited flat temperature coefficients of permittivity (TCɛ). The impedance spectroscopy analysis indicated that the non-Debye relaxation mechanism existed in BSBT–xBNT ceramics. BSBT–xBNT ceramics may have potential application value for the high-temperature capacitor.

Lead-free [(Bi0.5Na0.5)0.93Ba0.07]1-xLaxTi1-yZryO3 (BNBLTZ) ceramics were investigated for energy storage applications. In order to adjust its energy storage properties, the La and Zr co-doping contents varied at 0.01 ≤ x, y ≤ 0.04. BNBLTZ ceramics show a single phase perovskite structure without phase transition after La and Zr co-doping. The compact and uniform microstructure with similar grain morphology and different grain sizes is obtained. The remnant polarization and coercive field decrease with the increase of La and Zr additions, and the energy storage density increases drastically. The maximum energy storage density of 1.21 J/cm3 is obtained when x = 0.04 and y = 0.01. There are two dielectric anomalies at Tp and Tm due to the phase transformation. The results suggest that lead-free BNBLTZ ceramics should be good candidates for energy storage applications.

Thermal-induced self-degradation and recombination losses greatly impact the performance of inverted perovskite solar cells (PSCs). Herein, a multi-functional thermal management strategy based on ionic liquids (1-butyl-3-methylimidazole dibutyl phosphate, BMDP) is proposed for the first time to overcome these challenges for excellent thermal stability and efficiency in inverted PSCs. The BMDP can diffuse into grain boundaries (GBs) and stay at the surface perovskite film, resulting in efficient thermal management, trap passivation, ion migration elimination, hydrophobic improvement, as well as interface electric field enhancement. With the help of BMDP, the thermal conductivity of the perovskite film and the device at high temperatures were enhanced by 32.56% and 61.90%, respectively. In addition, the heat dissipation speed device was also accelerated. The power conversion efficiency (PCE) of the unencapsulated devices based on the intrinsically unstable MAPbI3/PCBM heterojunction can maintain about 90% of the initial value, whether at 85 °C for 1080 h, or in air (RH = 30 ± 5%, 25 °C) for 1440 h, which is one of the most reported stable results based on the thermally unstable MAPbI3/PCBM heterojunction to date. Furthermore, the high PCE can be improved greatly with this multi-functional thermal management, and the highest PCE of 21.98% and 23.25% have been achieved in the inverted devices based on MA/I and Rb/Cs/FA/MA/I/Br perovskite systems. [ABSTRACT FROM AUTHOR]