In this study, the phase transition behavior of (Bi0.5Na0.5)TiO3-BaTiO3 (BNT-BT) ceramics in different physical states (bulk and powder) was systematically investigated. High-temperature synchrotron X-ray diffraction revealed that BNT-BT ceramics with identical compositions show different phase transition temperatures (Curie temperature, TC) depending on their physical form. Specifically, powder samples showed higher TC compared to bulk samples. It is speculated that the significant differences in phase transition temperature between two physical states generate from variations in internal stress and mechanical constraints. In bulk ceramics, residual internal stress and lattice strain may destabilize long-range ferroelectric order, leading to a reduced TC. In contrast, powder samples can partially release internal stress through free surfaces, thus stabilizing the ferroelectric phase and resulting in a higher transition temperature.

This study presents a framework to analyze the grain-size effect in BaTiO3 ceramics by correlating domain wall (DW) density and lattice distortion at the DW. BaTiO3 ceramics with average grain size (GS) of 0.9-10 & micro;m were fabricated via conventional and two-step sintering methods. Following DC poling of 3 kV/mm at 80 degrees C, the piezoelectric charge constant (d 33) showed a maximum of 440 pC/N at GS of 1.2 & micro;m, due to an optimum DW density and lattice distortion at the DW. Both smaller and larger GSs relative to 1.2 & micro;m showed a decrease in d 33, attributed to reduced lattice distortion at the DW for smaller grains and decreased DW density for coarse grains. A similar trend was observed in the dielectric constant, free permittivity, coupling coefficient, elastic compliance, and piezoelectric voltage coefficient. Furthermore, the mechanical quality factor (Qm) evaluation revealed intrinsic and extrinsic contributions, with a maximum Qm of 140 at GS = 10 & micro;m. This framework provides a unified explanation for the grain-size-dependent electromechanical properties of BaTiO3 ceramics.

Highly 〈100〉 c -oriented 0.3BaTiO 3 –0.1Bi(Mg 0.5 Ti 0.5 )O 3 –0.6BiFeO 3 (0.3BT-0.1BMT-0.6BF) lead-free piezoelectric ceramics were fabricated via a reactive templated grain growth (TGG) method combined with additional hot-pressing during lamination. The previous issue of the decrease in the Curie temperature of ceramics fabricated by a TGG method due to undesired template—matrix reaction was thoroughly overcome by the use of the reactive TGG method. By optimizing experimental conditions such as the sintering temperature, doctor blade gap, and sintering time, a high relative density of >95% and a high degree of orientation F 100 of 90% were simultaneously achieved. The textured ceramics maintained a high Curie temperature T C of 450 °C, which was comparable to that of randomly oriented ceramics. Furthermore, the 90%-oriented ceramics exhibited an approximate 1.3-fold improvement in the large-signal piezoelectric coefficient (∼440 pm V −1 ) under unipolar electric fields compared to randomly oriented ceramics, offering a promising pathway for high-temperature, high-performance lead-free applications.

K(Ta0.5Nb0.5)O3 electro-optic transparent ceramics were fabricated using solid-state synthesis and a conventional sintering technique. The effects of the sintering temperature Ts and the excess KHCO3 content y on densification, crystal structure, microstructure and electric properties were investigated. Dense ceramics with a relative density of 97–98

We fabricated <110>(c)-oriented and randomly oriented 0.85(Bi0.5Na0.5)TiO3-0.15BaTiO(3) ceramics and investigated the effect of the grain orientation on depolarization and phase transition temperatures by measuring the temperature dependence of dielectric properties and synchrotron X-ray diffraction (XRD) patterns. Based on the dielectric measurements, the depolarization temperature of poled randomly oriented ceramics was 194 & ring;C; this temperature increased to 241 & ring;C with grain orientation. The XRD study revealed that depolarization occurred due to a phase transition from a single tetragonal phase to a mixture of tetragonal and pseudocubic phases. The temperature of the phase transition from the mixed phase to the single pseudocubic phase was also found to increase with grain orientation. Such increases in the depolarization and phase transition temperatures were attributed to the relaxation of internal stresses induced in the randomly oriented ceramics by the grain orientation.

Understanding how poling treatments enhance the functional properties of ferroelectric ceramics requires nondestructive visualization of strain, defects, and domain structures within individual grains in ceramics that are processed into a form suitable for mounting, without destroying them. Here, we establish a high-energy Bragg coherent X-ray diffraction imaging apparatus that enables nondestructive observation of a ∼1 μm-sized BaTiO 3 grain within a 0.3 mm-thick polycrystalline ceramic. This is achieved by employing a high-resolution detector and a new experimental hutch that satisfy the oversampling condition. The reconstructed three-dimensional images reveal grain morphology, domain configurations, and a shear-strain region accompanied by an adjacent lattice fault; notably, one grain exhibits a normal-fault–type displacement, rarer than the common reverse-fault type. Quantitative phase analysis yields local strain values of around 0.1%, comparable to the operating strains of piezoelectric materials. This approach provides a powerful tool for correlating microscopic structural changes with macroscopic property enhancements in ferroelectric ceramics.

We report experimental results on the temperature-dependent phase-matching properties of AgGa1-xInxSe2 with x = 0.315 for type-1 second-harmonic and sum-frequency generation in the 2.200-10.5910 & micro;m range. From these data, we derived a thermo-optic dispersion formula for x = 0.315. Using our recently published formula for AgGaSe2 (x = 0), we further extrapolated a companion formula for AgInSe2 (x =1) based on the standard interpolation of the linear susceptibility in the mixed chalcopyrite. The validity of this new set of index dispersion formulas was confirmed by reproducing earlier experimental results on temperature-tuned, type-1 cascade third-harmonic generation of a CO2 laser in AgGa1-xInxSe2 with x = 0.474, under angular noncritical phase-matching conditions.

The temperature-dependent evolution of the structural components in bulk and ground 87.5%(Bi 0.5 Na 0.5 )TiO 3 –12.5%BaTiO 3 (BNT–BT) ceramics was investigated using synchrotron radiation X-ray diffraction. Both the bulk and ground samples exhibited the coexistence of cubic ( Pm 3 ¯ m ) and pseudocubic ferrielectric ( P 4 bm ) components over a temperature range of 300–600 K. In bulk ceramics, tetragonal components ( P 4 mm ) with a large lattice strain abruptly appeared at the ferroelectric phase transition during cooling. In contrast, the ground powders retained a tetragonal component ( P 4 mm ) with a small lattice strain even at elevated temperatures, and both its volume fraction and lattice strain gradually increased with decreasing temperature over a wide temperature range, obscuring a distinct phase transition temperature. These results demonstrate that mechanical grinding modifies the evolution of the structural components and enhances the structural heterogeneity of BNT–BT ceramics. The diffuse transformation behavior observed in the ground powders was likely associated with the strain-induced stabilization of the ferroelectric structural component.

The effect of BaTiO3 (BT) ceramics texturing along < 111 > on piezoelectric and dielectric properties was investigated. Strongly < 111 > textured BT ceramics were fabricated using template grain growth technique with plate-like < 111 > templates. The influence of template content and sintering conditions on texture development was systematically examined. An optimized composition with 5 mol% template, sintered at 1300 degrees C for 5 h, achieved a high Lotgering factor (LF) of 95% and a relative density >= 95%. The dielectric constant (epsilon(r)) increased with the degree of texturing, reaching 3260 at an LF of 95%. Similarly, the piezoelectric charge coefficient (d(33)) increased with LF, reaching 227 pC/N after poling at 3 kV/mm for 10 minutes. This enhancement with increasing LF is attributed to crystallographic domain engineering induced by < 111 > texturing, which enables spontaneous polarization switching along three equivalent < 001 > directions under an applied electric field, thereby enhancing the piezoelectric and dielectric properties.

Organic ferroelectrics are attracting attention as flexible, lightweight, and environmentally benign alternatives to inorganic perovskite ferroelectrics. We synthesized and characterized a metal-free dielectric material, MDABCO (N-methyl-N '-diazabicyclo[2.2.2]octonium)(NH4)X3, by substituting the iodide ion (X = I) with nitrate (NO3). Heat capacity measurements conducted with a relaxation calorimeter (PPMS) indicated a phase transition (alpha -> beta) occurring near 273 K. Detailed differential scanning calorimetry (DSC) analysis revealed that the beta-phase is metastable and that a more stable phase (gamma-phase) exists. Single-crystal X-ray diffraction showed that, unlike the iodide analogue, the beta-phase adopts an antiferroelectric structure, attributed to hydrogen-bonding interactions that govern MDABCO molecular orientation. Dielectric measurements further identified a relaxation process in the alpha-phase associated with the rotational dynamics of MDABCO cations, underscoring the critical role of hydrogen bonding in modulating structure and dielectric behavior in all-organic perovskites.

We report experimental results on the temperature-dependent phase-matching properties of AgGa 1- x In x Se 2 with x = 0.315 for type-1 second-harmonic and sum-frequency generation in the 2.200–10.5910 µm range. From these data, we derived a thermo-optic dispersion formula for x = 0.315. Using our recently published formula for AgGaSe 2 ( x = 0), we further extrapolated a companion formula for AgInSe 2 ( x = 1) based on the standard interpolation of the linear susceptibility in the mixed chalcopyrite. The validity of this new set of index dispersion formulas was confirmed by reproducing earlier experimental results on temperature-tuned, type-1 cascade third-harmonic generation of a CO 2 laser in AgGa 1- x In x Se 2 with x = 0.474, under angular noncritical phase-matching conditions.

Temperature-dependent phase-matching conditions for nonlinear frequency conversion in AgGa 1– x In x Se 2 are studied using different CO 2 laser lines at 9.2714–10.5910 μm by varying the crystal temperature in the 20–180°C range.

Nitrogen vacancy (NV) centers in diamonds can function as quantum sensors for measuring magnetic fields, temperature, and stress with high sensitivity. They are useful in various biological applications, such as for measuring the local magnetic and electrical fields and signal propagation in tissues as well as their local interaction dynamics. However, to enable measurements suitable for medical applications, an observation system that can noninvasively map neural activity from the magnetic fields generated by brain nerve cells with high spatial resolution and sensitivity is required. We fabricated a vertical waveguide array in a diamond containing nitrogen vacancy (NV) centers with cell size dimension using a green femtosecond Bessel beam laser. The red emission from NV centers within the waveguide is confined inside the waveguide (typically with a cell size of 15 μm) by the total internal reflection at its walls. This enables efficient optical confinement and improves the light collection performance of the NV center emission. We have also developed a sensor—called the diamond micro-NV center array device (MAED)—that allows the observation of local magnetic field distributions and have measured spatial distribution of magnetic field with cell-size accuracy. This approach makes it possible to perform localized measurements of electrical and magnetic properties, as well as dynamic mapping of biological systems. This technological innovation holds a significant potential for the noninvasive observation of functional networks in cortical neurons.

CO2 reduction reaction (CO2RR) using a zero-gap reactor is attractive and is an attractive technology that is gaining attention for its potential to achieve carbon negativity. When using an anion exchange membrane for CO2RR, the pH of the anolyte solution changes due to the migration of acids produced in the cathode with the migration of alcohols, HCO3-, CO32-, and OH- also produced in the cathode. In addition, the alkali metal cations (K+) concentration decreases in the anolyte, which is also observed with the K+ migration from the anode to the cathode by electroosmosis. We evaluated this change by varying the KHCO3 and formic acid concentrations. The results will help us to identify problems and improve the reaction.

We are conducting research aimed at removing space debris through thrust generated by laser ablation, exploring the optimal laser for this purpose. To achieve this, we believe it is necessary to develop a simulator based on the principles of laser ablation that can estimate thrust under various conditions such as ultra-short pulses, infrared, and ultraviolet. Our research is advancing through experiments as the first step towards developing this simulator. In this work, we will mainly discuss the generated thrust and coupling factor using a Q-switched ns laser with harmonics.