In this article, the actuating performance for functionally graded piezoelectric materials (FGPM) using the \(d_{33}\) mode actuation is investigated. The material properties vary continuously across the thickness direction, according to a fraction volume power law distribution, so that top and bottom surfaces consist of pure PZTG and the mid surface is composed of pure aluminium. The percolation phenomenon is taken into account. The optimization of the interdigitated electrode (IDE) design for FGPM is performed using finite element analysis. Several design parameters (electrodes number, width and spacing) are considered to improve the produced displacement for a cantilever plate, and the use of multilayered IDE is intended. Results are discussed for several distributions of the components in the FGPM thickness. A comparison with the \(d_{31}\) mode actuation is presented.

Optical and photocatalytic applications of Al2O3 and TiO2 ceramics are limited, especially under visible light, due to their wide bandgap; so, this parameter plays an important and even decisive role in these applications. In the present study, Al2O3-TiO2 ball milled powders were sintered by spark plasma sintering (SPS) at 1573 K. The products were characterized using XRD, SEM, UV–Vis and electrochemical methods. The results indicated effective improvement in the light absorbing capability of the composites (up to 95%) under visible light and the decrease of the band gap down to 2.2 eV owing to the increase of oxygen vacancies, which was, in turn, due to the reduced atmosphere of the sintering process. In addition, formation of a new phase (Al2TiO5) during sintering greatly affected the absorption of Al2O3-TiO2 composites in the visible light region due to the increase in the fraction of the charge carrier separation centers. Photo-luminescence spectroscopy also showed that tialite formation could be effective in improving the charge separation efficiency.

In this work, it was aimed to synthesize and characterize rare earth metal-free cerium-based electrolytes that might be used in solid oxide fuel cells (SOFCs) by doping calcium, strontium, or magnesium to CeO2. For this purpose, CeO2, CaxCe(1-x)O(2−δ) (0.16 ≤ x ≤ 0.24), SrxCe(1-x)O(2−δ) (0.02 ≤ x ≤ 0.08) and MgxCe(1-x)O(2−δ) (0.07 ≤ x ≤ 0.13) were prepared by using citrate-nitrate combustion method. The solubility limits, microstructural and physical properties of the samples were characterized with XRD, SEM, TG-DTA and impedance analysis. It was found that all samples were in fluorite structure similar to the undoped ceria. The solubility limits of Ca2+, Sr2+ and Mg2+ were 21%, 6% and 12% (by mole) respectively based on XRD analysis results. The relative densities of sintered pellets at 1400 °C were more than 90%. Electrochemical impedance spectroscopy analysis, in which the ionic conductivities of the samples were measured, revealed that the Ca0.2Ce0.8O2-δ (CCO20) sample sintered at 1400 °C showed the highest ionic conductivity value of 4.47 x10-2 S.cm−1 at 800 °C. It was determined that the O2- ion conductivity decreased with the order of Ca2+ ≈ Sr2+ >> Mg2+. Conductivities increased with increasing dopant ratio, reached a maximum below the ratios of solubility limits, and then decreased. The obtained results showed that Ca or Sr doped electrolytes prepared by the citrate-nitrate method can show ionic conductivities close to the state-of-the-art Sm doped Ceria electrolytes. It has been determined that Mg doping is quite ineffective.

Piezoelectric nanogenerators (PENG) collect energy from the environment and biomechanical movements and convert this mechanical energy into electrical energy. They have become an attractive alternative to traditional rechargeable batteries for providing electrical power low energy portable devices. As PENGs became the center of attention in robots, wearable devices, medical equipment, and many other fields, the development of piezoelectric materials has become mandatory. This review reviews the basic information, structure, properties, and preparation methods of Barium Titanate, one of the most important PENGs, its development in recent years, and the progress towards high energy generation.

La0.6Sr0.4FeO3 ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been investigated according to dielectric measurements in the frequency range 10–1 - 106 Hz and the temperature range 93 - 313 K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model. This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects attributed to the heterogeneous structure of La0.6Sr0.4FeO3 grain boundary according to the morphological analysis. Such characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures.

The ferroelectric Ir/PZT/Pt and Au/PZT/Pt capacitor structures are studied by the electron beam induced current (EBIC) technique and the steady-state current–voltage dependencies. EBIC data reveal the change in the local field at the PZT/metal interfaces caused by migration of oxygen vacancies \({V}_{o}^{**}\) under an action of applied electric field. Ir/PZT and Pt/PZT interfaces block \({V}_{o}^{**}\) movement causing their accumulation near the cathode interface. An electrons injection from the metal cathode to the PZT leads to formation of induced p–n junction. The steady-state leakage current in this case is well described by modified equation for the p-n diode, which considers an action of the counter electric field caused by electrons injection. In the case of transparent for oxygen vacancies Au/PZT cathode oxygen vacancies leave the PZT bulk and current–voltage dependence demonstrates a region of negative differential conductivity at high electric fields. The proposed p–n junction formalism can be used for engineering of PZT-based devices.

Polycrystalline samples of Bi4V2(1-x)Cu2xO11-3× were prepared by solid state reaction method. Thrust of the work is to stabilize high temperature conducting γ-phase at room temperature. XRD and DSC analysis indicates orthorhombic ‘α’ phase for x ≤ 0.08 to tetragonal γ-phase transition for x = 0.1, at room temperature. Variations of real and imaginary impedance as well as complex electrical modulus with frequency are reported. Experimental impedance spectroscopic data was theoretically fitted and equivalent circuits are proposed. Nyquist plots revealed contribution from grain as well as interface. Variations of impedance, dielectric permittivity and AC conductivity as a function of frequency at selected temperatures are reported. The AC conductivity was fitted with Jonscher’s power law and the power law exponent (η) was found to be < 1, indicating that the conduction process follows CBH mechanism. The dielectric behaviour was found to follow UDR model. Cu2+ ions was observed to introduce defects and oxygen vacancies, space charge accumulation, reduction in dielectric permittivity and increase in the conductivity as high as up to 0.45 S·cm−1 for the expected γ-phase.

The substitution of Dy3+ ions in the M-type hexaferrite structure has been successfully synthesized by sol-gel combustion method according to the formula SrDyxFe12-xO19 (x = 0.0, 0.08, 0.16, 0.24, 0.32, and 0.40). The XRD analysis confirmed the formation of single-phase M-type hexagonal structures up to x = 0.24 compositions. The average crystallite size for the SrDyxFe12-xO19 samples ranges from 90.64 to 290.04 nm, whereas the value of the lattice parameters 'a' and 'c' vary from 5.8590 - 5.8879 Å and 22.9675 - 23.0761 Å, respectively. Scanning electron microscopy (SEM) was used for morphological analysis. Due to ceasing effect of polarization, the dielectric constant decreases in the higher frequencies. The SrDyxFe12-xO19 hexaferrites exhibit non-Debye type dielectric relaxation behavior confirmed by complex impedance spectroscopy (CIS) investigation. The SrDyxFe12-xO19 samples can be utilized as a promising material for various device applications due to a decrease in dielectric loss and an increase in dielectric constant with increasing Dy3+ ions concentration.

Piezoceramic composition (1-z) (0.67Bi1.05FeO3–0.33BaTiO3)–zBi(Mg0.5Zr0.5)O3 (z = 0.00−0.10) were framed in this work. Regular firing technique succeeding by quenching method was applied. Effect of Bi(Mg0.5Zr0.5)O3, abbreviated as BMZ, modification on structural and electrical properties were systematically analyzed. A large-field piezoelectric coefficient (Smax/Emax = d33*) of 560 pm/V at 4 kV/mm and relatively small hysteresis (~ 28%) were obtained. The possible enhancement in strain, d33 and Pr values near the optimal compositions z = 0.060, 0.080 can be ascribed to the augmented anharmonicity of lattice vibrations that may facilitate the flexiblity (at unit cell level) of these narrow compositions and triggers the enrichment of piezoelectric properties. A large piezoactuation constant with relatively low hysteresis loss and high working temperature (Tm around 415 οC) without unwanted depolarization temperature Td made the investigated piezomaterial promising for the ceramic actuators’ applications. Unlike BNT-based systems, where mixed ergodic relaxor (ER) and nonergodic relaxor (NR) states are supposed to generate high strains, in the present BF-based ceramics, based on obtained results, BMZ-modified BF-BT materials are hypothesized to spontaneously switch from a high-temperature ER state to a ferroelectric state without transitioning to an intermediary NR state.

NaNbO3-based antiferroelectric (AFE) ceramics have the prominent advantages of stable performance and low cost. However, its energy storage property is often remarkably limited by the hysteresis of the antiferroelectric to ferroelectric phase transformation. In this work, 0.88Na(Nb1−xTax)O3–0.12Bi0.2Sr0.7TiO3 (x = 0–0.075) antiferroelectric ceramics were synthesized using a conventional mixed oxide route. Ta5+ were completely dissolved into the lattice of 0.88NaNbO3–0.12Bi0.2Sr0.7TiO3 to form a pure perovskite structure. With increased Ta content, the AFE orthogonal P phase was replaced by AFE orthogonal R phase progressively. Meanwhile, the dielectric constant curve showed relaxor-like properties. As a result, slender P–E curves with reduced hysteresis loss and decreased residual polarization were achieved. Interestingly, a large recoverable energy storage density (Wrec ~ 2.16 J cm−3) and high energy storage efficiency (η ~ 80.7%) were obtained simultaneously under a low driving electric field of 15 kV mm−1 at doping ratio (x) of 0.075. In addition, the 0.88Na(Nb0.925Ta0.075)O3–0.12Bi0.2Sr0.7TiO3 sample exhibited excellent temperature stability, indicating an ideal candidate in future pulsed power capacitor.

The preparation of CuCo2O4 material with a suitable phase structure and grain size can improve its lithium storage performance. In this paper, CuCo2O4 hexagonal nanocrystal were successfully obtained by molten salt modified urea combustion method. Compared with the traditional high temperature solid state methods such as combustion method, rheological phase method and precipitation method, this method maintains the advantage of simple operation, and the particle size of the sample is smaller. The effect of heat treatment temperature on the lithium storage performance of CuCo2O4 was also studied systematically in this paper. The result shows that 800 ℃ is the best heat treatment temperature for CuCo2O4, and the sample synthesized by the molten salt urea combustion method exhibited the best electrochemical properties with a specific capacity of 705 mA h g-1 after 100 cycles under a constant current of 200 mA g-1 in the voltage range of 0.01-3 V. Therefore, a new strategy of high temperature solid state preparation has been developed in this paper, and the CuCo2O4 synthesized by this method is a promising anode material for lithium ion battery application.

Nanocrystalline BiFeO3 was synthesized utilizing two distinct techniques: auto-combustion and ceramic. A unique auto-combustion process employing glycine as a fuel has been used to synthesize single-phase BiFeO3 nanoparticles. Well mixed metal nitrates combust, producing BiFeO3 nanoparticles, which crystallize in a rhombohedral perovskite structure. The average particle size of 16 nm was estimated using Rietveld refinement of the X-ray diffraction data. The X-ray diffraction data for the solid-state prepared sample shows the formation of BiFeO3 with the same rhombohedral perovskite structure with an average particle size of 101 nm with additional secondary phases corresponding to Bi2Fe4O9/Bi2O3 and Bi25FeO39. By increasing the sintering time Bi2Fe4O9/Bi2O3 phase disappeared after 3 h of heating and reappeared again after 5 h of sintering. The changing of sintering time was not able to reduce the Bi25FeO39 formation. The TEM estimated average particle size confirms the XRD analysis. M(H) hysteresis loop shows a G-type magnetic structure. Due to the small particle size, the periodicity of canted spins was broken, and the magnetization of the auto-combustion prepared sample is approximately eight times greater than the ceramic prepared one. The importance of pure phase BiFeO3 came from its potential applications in sensors, data storage, spintronics devices, and reports of greatly enhanced ferroelectricity in epitaxially strained thin films.

Oxygen non-stoichiometry profoundly impacts the electrical, magnetic, and catalytic properties of metal oxide. Limited by the low mass and volume of thin oxide films, conventional quantification methods, such as thermogravimetry, are not directly applicable. While chemical capacitance has been successfully applied to monitor oxygen non-stoichiometry in thin oxide films, detailed a-priori understanding of the defect chemistry is often very helpful in its interpretation. In this study, changes in non-stoichiometry in Pr doped CeO2 (PCO) thin films are measured by coulometric titration. I-V titration measurements are performed on electrochemical cells, over the temperature range from 550 to 700 ℃, oxygen partial pressure range from 10-4 to 0.21 atm, and bias range of -50 mV to 50 mV, to extract changes in stoichiometry. The results agree well with values obtained by chemical capacitance, demonstrating the utility in applying coulometric titration to investigate oxygen non-stoichiometry in oxide thin films.

The reaction sintering, without calcination and following re-grinding, has been paid increasing attention. Non - stoichiometric Li2Mg3Sn1 − xO6 (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were successfully gained through reaction sintering process in the study, and its phase composition, morphology and dielectric characteristics were studied. This XRD patterns of Li2Mg3Sn1 − xO6 samples prepared after sintering at 1,305 ℃ for 6 h indicates that green bodies are mainly composed of Li2Mg3SnO6 phase, accompanied by the second phase of Mg2SnO4. A host of pores, elliptic - like grains and wrinkle - like grains were visibly observed from the SEM images of Li2Mg3Sn1 − xO6 ceramics, which is because of the severe volatilization of Li elements at high temperature. The apparent density, relative permittivity, quality factor and temperature coefficient of resonant frequency of samples will be devastate owing to porous morphology and Mg2SnO4 phase to a large extent. Finally, when x = 0.08, Li2Mg3Sn0.92O6 ceramics have optimal dielectric performances: εr = 9.133, Q×f = 55,429 GHz, τf = -36.1 ppm/℃.

CaCu3Ti4O12 ceramics have great dielectric constant, excellent temperature stability and good frequency stability. However, due to high dielectric loss, its practical application in engineering is hindered. In this paper, Na0.25Bi0.25LaxCa0.5-3x/2Cu3Ti4O12 (NBLCCTO) ceramics were prepared by solid phase synthesis. The effects of sintering temperature and La content on dielectric properties of NBLCCTO ceramics were studied. The results show when the sintering temperature is 1030℃ and La content is 0.05, NBLCCTO ceramics show better dielectric properties. Its dielectric constant has εr = 22,231 at 1 kHz and its dielectric loss is 0.0546 at 10 kHz. Appropriate doping of La can lead to grain refinement and enlarge specific surface area of grain boundary, thus increasing resistivity and reducing dielectric loss. Therefore, NBLCCTO ceramics have lower dielectric loss than Na0.25Bi0.25Ca0.5Cu3Ti4O12 (NBCCTO).

A well-designed matching layer attached to a transducer is an effective method to obtain broad bandwidth. In practical applications, the optimal material parameters and geometric parameters for the matching layer are required to be calculated precisely. In this paper, we propose a fluid–structure interaction model for vibro-acoustic analysis of the transducer. An analytical solution to determine the electrical impedance of a transducer with a matching layer immersed in water is derived. The influence of matching layer on the performance of the transducer is demonstrated clearly. To verify the proposed model, a 1–3 piezoelectric composite transducer with a matching layer according to the our proposed model is fabricated. Consequently, the theoretical model we proposed can accurately predict the electrical impedance of the transducer with a matching layer. According to the model, the optimal thickness and acoustic impedance for the matching layer to expand the conductance bandwidth of the transducer can be figured out accurately. In addition, our proposed model also provides a reference for designing a transducer with a matching layer.

In this study, we developed an electrochemical sensor for sensitive detection of 4-NP in solution by using polyol-assisted co-precipitation process prepared copper doped cerium oxide nanoparticles (CeO2:Cu NPs). Phase purity, crystal structure, and morphology of the as-prepared nanoproduct were examined by X-ray diffraction and transmission electron microscopy images. Chemical composition was determined by energy dispersive x-ray analysis(EDX). UV/Visible spectrum was measured to determine the optical absorption properties and bandgap energies of the material. The prepared CeO2:Cu NPs were pasted on a glassy carbon electrode(GCE) to measure the electro-catalytic performance and further examining their sensing application through determining the 4-nitrophenol (4-NP) concentrations. The performance of the constructed electrode was assessed by cyclic voltammetry(CV) and electrochemical impedance spectroscopic(EIS) methods. The Cu doped CeO2 NPs exhibited demonstrated excellent electrochemical performance in the presence of 4-NPs in a 10 pH phosphate buffer solution (PBS). The voltammetry-acquired kinetic evidence shows that 4NP electro-oxidation is a strictly diffusion-controlled process and that four electrons are involved in the reaction mechanism. The constructed CeO2:Cu/GCE illustrated a high linearity range from 7.18-5000µL, a good detection limit (7.18 µL), with high sensitivity 1.4 μA mmol−1 L. The reproducibility of the fabricated electrode was also monitored through nine consecutive CV cycles to measure their stability.

Poly (vinylidene fluoride- hexafluoroproylene) PVDF-HFP has been employed as a host polymer because of its strong chemical resistance, mechanical and dielectric properties and low cost. However, further changes employing other polymers, nanomaterials, additives and fillers to improve the properties of the host polymers are of significant interest. TiO2 has gained a lot of attention because of its high k dielectric and photo catalytic capabilities. Graphene oxide (GO) has received a lot of attention because of its larger mechanical strength, dielectric behavior and other qualities. Using the doctor blade coating process, varied amounts of TiO2 and GO were successfully integrated into PVDF-HFP to form composite films. The XRD result reveals that TiO2/GO has been successfully incorporated into the PVDF-HFP polymer matrix, while FTIR, SEM experiments have demonstrated the effectiveness of TiO2/GO fillers on PVDF-HFP film. AC impedance spectroscopy reveals the dielectric behavior and resistivity of polymer nanocomposite film. The film has been tested for its loading bearing capacity during electroadhesion with different applied voltages. The maximum load bearing capacity based on electroadhesion has been estimated.Graphical abstract

Structural, morphological, FTIR, optical and photoluminescence (PL) measurements of Zn1-xRExO nanoparticles with RE = Y, La and x (0.00 ≤ x ≤ 0.20) are reported. The wurtzite structure is confirmed for all samples and the lattice parameters, Zn–O bond length, porosity, crystallite size, lattice strain and residual stress are increased by increasing x to 0.20, but they are higher for La samples than Y. The grain sizes are 180, 330, and 460 nm for the pure, Y and La samples. The addition of RE to ZnO generally shifts FTIR absorption peaks, Debye temperature, and elastic modulus to higher values, but the shift is higher for La samples than Y. Although excitonic energy is constant for all samples, the energy gap Eg was increased by increasing x to 0.20, but it is higher for La samples than Y. Furthermore, the dielectric lattice constant, density of charge carriers, and electrical conductivity are increased by increasing x to 0.10, followed by a decrease to 0.20. The opposite behavior is true for dielectric loss and optical conductivity. The PL intensity shows four continuous visible peaks of near UV, blue, green, and red. Interestingly, the intensity of blue emission is greater than that of near UV, such that [(Iblue/IUV)] > 1]. Furthermore, for x > 0.10 samples, there is another lowest intensity IR emission peak centred at 824 nm (1.507 eV). These results are well explained and strongly recommend the RE doped samples for the applications of optoelectronic and high-power operating devices. To our knowledge, the present investigation probably has never been reported elsewhere.

Ba0.85Ca0.15Zr0.1Ti0.9O3-x wt% CuO (BCZT-xCu) lead-free piezoelectric ceramics were designed and synthesized using a traditional solid-state reaction method to improve both the relaxor behavior and the electrical properties of BCZT lead-free piezoelectric ceramics. The Cu2+ diffuses into the BCZT lattice and forms ABO3 perovskite solid solution. Additionally, X-ray diffraction patterns and Raman spectra reveal that the introduction of CuO causes phase transition from the O-T phase coexistence to the O phase in BCZT-xCu. SEM displays that BCZT-xCu has a well microstructure at CuO doping amount between 0.5 wt% and 1 wt%. With the increasing CuO content, the orthorhombic-tetragonal (TO-T) phase transition shifted towards higher temperature, while Curie temperature (Tc) shifted towards lower temperature. Moreover, the dielectric diffusivity γ increases from 1.63 to 1.92 as x increases. Results indicate that optimal electrical properties, namely d33 = 315 pC/N, kp = 34%, εr = 3213, tanδ = 2.71%, Pr = 7.45 µC/cm2 and Ec = 2.75 kV/cm are achieved in the 1 wt% CuO added ceramic sintered at 1250°C for 2 h.