BaTiO3 piezoelectric ceramics are mainly used for capacitors. However, their potential as sensors and transducers remains limited due to their moderate piezoelectric sensitivity and energy conversion efficiency. Furthermore, most dopants used for enhancing piezoelectricity often reduce the Curie temperature, restricting thermal stability. In this work, aluminium-doped BaTiO3 ceramics were synthesized by solid-state reaction with compositions: (1-x) BaTiO3-xBaAlO(2.5) (x = 0-0.05). The objective was to investigate the role of Al on structural, dielectric, electromechanical properties, and electrical fatigue cycling. Al incorporation modified sintering kinetics and created oxygen vacancies, thereby influencing lattice parameters, grain growth, and electromechanical properties. At x = 0.04, the ceramics showed optimal performance with: d(33)= 290 pC/N, d(33)*= 297 pm/V, kp= 38%, Qm= 72, g(33)= 12.10(-3) Vm/N and figure of merit d(33).g(33)= 3.5 & times; 10(-12) m(2)/N, while maintaining a Tc of similar to 122 degrees C and a Pr retention of 92.8% after 10(6) cycles(.) These results highlight aluminium-doped BaTiO3 as a well-balanced, lead-free alternative for piezoelectric applications.

The preparation of porous yet mechanically stable centimetric monoliths remains challenging using traditional methods. Herein, hierarchical SBA-15-based porous monoliths, with three levels of porosity (micro- and mesopores from the pores arrangement of the silica structure, and macropores from the replication of polymer beads), were prepared by simple inverse-opal technique. Though the addition of bentonite and proper thermal treatment, solids with specific surface areas above 300 m2/g and resistance toward compression above 50 N were obtained, which is coherent with a use as heterogeneous catalyst supports.

The research focuses on developing a piezoelectric nanogenerator through electrospinning technique, which is known for its efficiency in creating flexible piezoelectric membranes. We chose a lead-free material, iron-doped zinc oxide (ZnO-Fe), for its significant PolyVinyl Alcohol (PVA) dielectric and piezoelectric properties. our work began with the synthesizing of iron-doped zinc oxide (Zn0.988Fe0.012O) nanopowders using the sol-gel method, then mixing them in varying quantities with the PVA (PolyVinyl Alcohol) matrix to obtain a polymer suitable for building flexible piezoelectric nanowire membranes. Based on characterizations carried out on the various flexible piezoelectric structures, we chose the 7.5% by mass ZnO-Fe/PVA composite to create a voltage nanogenerator by applying manual deformation to the structure, whose output voltage visualization, using an oscilloscope, showed a maximum value of, 5.3 volt illustrating the direct effect of piezoelectricity. To enhance these results, we placed the device on a medical hand rehabilitation pad to indicate a patient's diagnosis, with the output voltage obtained estimated at around 1.8 V for a force of 10 N. The experimental results obtained show the best performance of the sensor based on the PVA/ZnO-Fe composite, in terms of flexibility and output voltage, with low costs and a simple method that's easy to implement.

This study combines first-principles Density Functional Theory (DFT) calculations and experimental analysis to investigate the impact of Sr-doping on the structural, electronic, and piezoelectric properties of Ba1xSrxTiO3(BST) perovskites at different Sr concentrations (x = 0, 0.125, 0.25 theoretically; x = 0, 0.1, 0.125, 0.15, 0.2, 0.25 experimentally). Theoretical results using the Wien2K package show that increasing Sr content induces a phase shift from tetragonal phase (ferroelectric) to cubic phase (paraelectric), confirmed by XRD analysis, which also reveals an increase in grain size. Key piezoelectric parameters, including remnant polarization (Pr), piezoelectric coefficient (e33), and piezoelectric constant (d33), theoretical predictions closely align with experimental findings. With Sr addition, Curie temperature and electromechanical coupling factor kp (%) decrease, minimizing BST's applicability for piezoelectric applications. Nonetheless, P-E hysteresis analysis highlights its potential for energy storage due to residual and saturation polarization. Electronic studies indicate that Sr doping narrows the band gap, suggesting BST's promise for optoelectronic, solar cell, and semiconductor applications. These findings demonstrate the multifaceted potential of Sr-doped BaTiO3, driven by Sr's influence on its structural, piezoelectric, ferroelectric, and electronic properties.

The incorporation of strontium into Ba1-xSrxTiO3 compounds has a significant impact on their structural, electronic, optical, and mechanical properties. This study presents an analysis based on first principles calculations using density functional theory (DFT) to study the effects of strontium doping by varying Sr concentrations. The evolution of the structure, electronic band structures, optical and mechanical properties is examined to understand how Sr doping influences the fundamental characteristics of the material. The results highlight that Sr doping provides valuable information for tailored design of perovskite-type materials, thus optimizing their properties for various technological applications.

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 mu m, 63 mu m and 140 mu m respectively for fully dense, powder and pre-sintered assembly approaches.

In order to enhance the thermal performance of two-phase fluid loop devices, the purpose of this study is to investigate the benefit of using a bilayer wick in a capillary evaporator.In a homogenous wick, the porous structure characteristics present an intrinsic competition between increasing the capillary forces and reducing the pressure drop.Our investigation focuses on studying heat and mass transfer in uniform and bilayer ceramic wicks with the same porosity. The findings highlight the interest of a bilayer ceramic wick with a pore diameter gradient. This configuration exhibits heightened capillary pumping without compromising liquid pressure drop, leading to improved thermal performance in the evaporator.Our results demonstrate that opting for a bilayer ceramic with a pore diameter gradient can save up to 25 °C at the casing temperature and reach up to 1430 W/m²K−1 as heat transfer coefficient for a 70 W heat load value.

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 μm, 63 μm and 140 μm respectively for fully dense, powder and pre-sintered assembly approaches.

In this study, the humidity detection properties of the ceramic with composition (Na0.5Bi0.5)0.94Ba0.06TiO3, noted (NBT-06BT), were investigated. The NBT-06BT ceramic was synthesized by the semi-solid method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The NBT-BT ceramic material sintered at 1100 ?C, crystallizes in the tetragonal system without any secondary phase and presents a heterogeneous distribution of polyhedral shaped grains with open intergranular porosities. The electrical and dielectric properties investigations show that the NBT-06BT ceramic material exhibits excellent humidity detection characteristics such as high sensitivity, good linearity and narrow hysteresis. The impedance decreases by three orders of magnitude when the relative humidity increases from 15 % to 90 % at 100 Hz. The maximum hysteresis value of the sensor is 4.69 % RH. The response time and the recovery time are about 68 s and 125 s respectively. Moreover, the sensing mechanism has been discussed in detail by analyzing the complex impedance spectra. These results indicate the potential application of the ceramic material NBT-06BT as a humidity sensor.

This study reports the preparation of highly porous, SBA-15-based monolithic materials with pore sizes spanning over four scales (micro-/meso-/small macro-/large macro-pores). Two approaches were explored. The first one involves the preparation of PMMA scaffolds obtained from chemically-bonded beads and their further infiltration using SBA-15 slurries with suitable viscosity; while the second one directly uses the same amount of PMMA beads dispersed within the slurries. Emphasis was given to the comparison of the textural, structural, and mechanical properties obtained following each approach. Then, application of a thermal consolidation step and its influence over the monoliths properties was investigated, with an optimum observed at 950 degrees C. The second method systematically allowed reaching higher mechanical resistances (86 vs 32 kPa at 950 degrees C) for comparable specific surface areas (274 vs 290 m(2)/g at 950 degrees C), however at the expense of smaller macropores and lower ordering in the monoliths.

This study was devoted to the understanding of the influence of MgAl2O4 ceramic properties on their ballistic performances. By modifying the processing parameters, ceramics with different microstructures were obtained. Among them, a transparent MgAl2O4 spinel with an in-line transmission between 77% and 83% in the visible range, an average grain size of 8.6 mu m and good mechanical properties (11.3 GPa in Knoop hardness and 2.5 MPa root m in fracture toughness) was produced. A thorough characterisation of the ceramics was accomplished in order to establish a link between microstructure, mechanical properties and ballistic protective performances against an armour piercing projectile of calibre 7.62x51 mm. The ballistic evaluation demonstrated the advantage of using a spinel layer as the strike face to stop a threat, while reducing drastically the thickness and the areal density of the transparent multilayer, compared to a simple glass armour. MgAl2O4 spinel with fine grains presented a better combination of mechanical properties compared to coarser microstructures, hence a better potential to damage a projectile at the impact.

A series of zirconium-based metal-organic frame-work (MOF) nanocrystals (95-211 nm) displaying sulfonate functions (UiO-66-SO3H) was prepared in N,N-dimethylforma-mide (DMF)-the conventional solvent-and water, and their physicochemical properties were thoroughly investigated. In particular, X-ray diffraction results suggest that upon replacing DMF with water, the resulting MOF crystal structure presents a highly defective structure belonging to the space group Im3 of typical Fm3m. The acid catalysts were applied to the fructose dehydration into 5-hydroxymethylfurfural (5-HMF). Complete conversion of fructose over UiO-66-SO3H prepared in water was reached after only 30 min at 100 degrees C, in line with its stronger Bronsted acidity. In comparison, its counterpart prepared in DMF showed only 30% fructose conversion. Moreover, the intrinsic catalytic effect at 80 degrees C was only observed with the water-based UiO-66-SO3H. Without reactivation of the catalyst, recycling tests demonstrated the preservation of its structural integrity upon nine consecutive cycles, while a gradual loss of the catalyst activity was attributed to the humin adsorption on the MOFs.

In this work, we investigate the effect of lithium and aluminium co-doping (0, 0.1, 0.2, and 0.3 mol%) on the phase formation, microstructure, dielectric, and electrical properties of (Ba0.85Ca0.15) (Ti0.90Zr0.10)O3 ceramics prepared by solid state reaction method. Rietveld refinement of X-ray diffraction patterns reveals the coexistence between the orthorhombic (Amm2) and tetragonal (P4mm) phases in all samples, and the amount of tetragonal phase increased with increasing Li and Al content. All ceramics reveal dense microstructures having relative density ~ 94–98% and the average grain size is significantly reduced by increasing Li–Al content from 0.1 to 0.3%. The temperature dependence of dielectric constants at different frequencies exhibited diffuse phase transition behaviour with no frequency dispersion. The refined grains and high density of BCLAxTZ ceramics leads to an improvement of dielectric properties, the composition BCLA0.3TZ exhibits excellent dielectric properties [ε = 7712.98, tan(δ) = 1.49 at.% 1 kHz]. The conduction mechanism have been investigated by means of impedance spectroscopy at various temperatures (100–450 °C) and the values of resistance, and conductivity, associated with the grain and grain boundaries were evaluated. When increasing the Li–Al content, an increase of dc conductivity was observed throughout the whole explored temperature rang. The appearance of two semicircles in Nyquist plots suggests the contribution of both grain as well as grain boundary contribution to overall electrical behavior in all samples. The grains effect is gradually replaced by grain boundaries effect with increasing temperature. The frequency dependence of ac conductivity was wellfitted according to Jonscher’s power law.

In recent years, Mg-Al spinel ceramic has been in the spotlight due to its large transparency range and good mechanical properties. The aim here, was to control the state of agglomeration of powder to improve densification behaviour and consequently optical and mechanical properties of the ceramics. Commercial powder with a small particle size was used and exhibits poor flowability, which was found to be detrimental to shaping and led to a translucent ceramic with an opaque crown. The powder was granulated by spray drying and the influence of the molecular mass of added polyethylene glycol on the granulate size, compaction and finally sintering behaviour was investigated. Special attention was paid to the differences in rheological behaviour of powders, which was thoroughly characterized with a FT4 powder rheometer. Agglomeration of powder improved in-line transmission at 650 nm up to 71% compared to 3% for ceramic from as-received powder.