Journal of Electroceramics最新文献

Ternary of PZN-xPZT relaxation ferroelectric ceramics were successfully prepared by conventional solid-phase reaction. With the increase of Pb(Zr, Ti)O₃ (PZT) content, XRD analysis shows a gradual decrease of the inclusion crystal phase and a decrease in the formation of secondary phases such as Zn(NbO₃)₂, leading to a more homogeneous phase structure, which is conducive to the improvement of piezoelectric properties. SEM images and densitometric measurements show a decrease in grain size and an increase in the degree of densification of the ceramics, which contributes to the enhancement of the ability of reorientation of electrical domains and thus the improvement of piezoelectric response. The 0.4PZN-0.6PZT ceramic samples demonstrate favorable grain sizes and exhibit the following optimal properties: T_c = 272 ℃, d₃₃ = 570 pC/N, k_p = 0.67, ε_r = 2175, and tanδ = 1.6%. However, the ceramic sample of 0.45PZN-0.55PZT has better comprehensive properties (T_c = 261 ℃, d₃₃ = 443 pC/N, k_p = 0.59, ε_r = 1908, tanδ = 1.7%, P_r = 37.3 µC/cm², P_s = 30.2 µC/cm², E_c = 1.08 kV/mm). PZN-xPZT ceramics are well known for their excellent dielectric, Curie temperature, phase boundary modulation, piezoelectric and ferroelectric properties and are widely used in sensors and transducers.

Researchers are actively prioritizing the development of ecologically friendly and energy-efficient materials for renewable energy devices, such as thermoelectric generators, to tackle the upcoming energy concerns. We have performed an extensive examination of the structural, phonon, electronic, thermoelectric, and thermodynamic properties of Cu-based chalcogenides TMCu₃S₄ (TM = V/Nb/Ta) for their prospective application in renewable energy technologies. The use of the GGA method within the framework of density functional theory (DFT) enables a thorough examination of exchange and correlation energy potentials using first-principles computations. Based on the computed structural parameters, it is evident that TaCu₃S₄ is the most stable compound among TMCu₃S₄ (TM = V/Nb/Ta) due to its lowest ground state energy. TB-mBJ produced improved energy bandgaps of VCu₃S₄, NbCu₃S₄, and TaCu₃S₄ are 0.575, 0.725, and 0.824 eV, respectively. The figure of merit (ZT) values for VCu₃S₄, NbCu₃S₄, and TaCu₃S₄ are 0.997, 0.946, and 0.943, respectively, at 50 K for constant chemical potential. These values render them exceedingly suitable for utilization in thermoelectric (TE) devices. The thermoelectric properties of Cu-based chalcogenides TMCu₃S₄ (TM = V/Nb/Ta) indicate that these materials have great promise for energy-related applications. The thermodynamic analysis reveals that the TMCu₃S₄ (TM = V/Nb/Ta) chalcogenide materials are thermally stabile.

The need for microwave dielectric ceramics is steadily growing along with the rapid advancement of wireless communication technology. The preparation of Li₃Mg₂NbO₆-xwt% LiF-TiO₂-CaF₂ (LMN-LTC, x = 4, 6, 8, 10) ceramics was carried out using the solid-state reaction method. The two-phase structure of the LMN-LTC ceramics was shown by XRD investigation, with the main phase being LMN and the second phase Ca(TiO₃). Due to the influence of additive LTC, the microwave dielectric properties of the LMN ceramics, especially the temperature stability were successfully regulated to near zero. The LMN ceramic with the addition of 6wt% LTC sintered at 1050 °C for 6 h exhibits outstanding microwave dielectric properties: ε_r = 13.0, Q × f = 42,000 GHz, τ_f = 1.76 ppm/°C. It is shown that LMN-6wt% LTC ceramic is promising for wireless communication applications.

This study examines how controlled doping of trivalent cations (Cr³⁺) at manganese (Mn³⁺) sites influences the structural, microstructural, vibrational, magnetic, and dielectric properties of LuMn_1 − xCr_xO₃ (0 ≤ x ≤ 0.08) compounds. These compounds were synthesized using conventional solid-state reaction techniques. Rietveld-fitted X-ray diffraction reveals hexagonal crystal symmetry (P₆₃cm space group) with reduced lattice parameters and volume due to Cr doping and ionic size mismatch. Room temperature Raman spectra show phonon peak shifts and reduced mode intensity, indicating structural disorder or internal stress in all samples. The magnetization outcomes reveal a weak ferromagnetic property across all samples, which can be enhanced with higher concentrations of Cr ions. The frequency-dependent dielectric properties and loss tangent (tan δ) at 300 K in all examined compounds demonstrate a decrease in dielectric constant and an increase in loss tangent. These changes are attributed to the double exchange interaction between Mn³⁺-O-Cr³⁺ cations, supported by the metallic character’s emergence. Our findings on improved magnetization and adjusted dielectric parameters represent progress in understanding multiferroic compounds.

Entropy-stabilized ceramics have attracted researchers significantly due to their potential vast multi-functional applications in various engineering fields. The present study emphasizes the synthesis, sintering temperature, Raman, and electrical behavior of a spinel (CoAlFeNTi)₃O₄ high entropy oxide (HEO). The HEO is synthesized through the modified solid-state reaction method at two different sintering temperatures (1100 °C and 1250 °C) and characterized further with the XRD, Raman, and SEM for structural and microstructural behavior. XRD analysis confirmed the formation of a single cubic spinel phase with the Fd-3 m space group. In addition, Raman analysis also confirmed that the synthesized HEOs have a spinel structure with an inverse spinel nature. With the enhancement of the sintering temperature, XRD analysis indicates that the crystallinity and crystallite size of the HEO enhanced. The current density (J) versus applied electric field (E) characteristics displayed that both 1100 °C and 1250 °C sintered HEOs possessed leakage current density at zero applied electric field and an ohmic conductance of (:4.59times:{10}^{-10}) mhos/cm and (:3.43times:{10}^{-10}) mhos/cm respectively. Moreover, J - E characteristics also showed that the enhancement of sintering temperature enhanced the resistive switching behavior of the different temperature sintered spinel HEOs. This improved resistive switching behavior in the J-E curve indicates that the synthesized spinel HEO can find potential application in resistive switching memory devices.

We introduce a high surface area sensor composed of Co₃O₄ nanoparticles (NPs) embedded within porous ZnO nanofibers (NFs), exhibiting a notable response to acetone. Initially, we synthesized polyvinylpyrrolidone (PVP) NFs containing zinc and cobalt salts via a simple electrospinning method. Subsequently, the calcination of the PVP NFs resulted in the formation of Co₃O₄ NPs embedded within the porous ZnO NFs. The heterostructure material demonstrated a significant response to 100 ppm acetone detection, with a ratio of electrical resistance in air (R_a) to that in the presence of gas (R_g) reaching 111 at its optimal operating temperature of 275 °C. Furthermore, it exhibited stable performance under high relative humidity conditions.

This study investigates the microwave dielectric and shielding properties of MgTiO₃-based solid solutions across the K (18–26.5 GHz) and Ka (26.5–40 GHz) frequency bands. Synthesized via a conventional solid-state mixed oxide route using MgO and Mg(OH)₂ as raw materials, the dielectric properties of MgTiO₃ and Mg(Ti_0.95Sn_0.05)O₃ solid solutions varied with composition and raw material. Results showed that MgO-based materials exhibited higher relative permittivity (ɛ_r) and loss tangent (tan δ) compared to Mg(OH)₂-based materials. Furthermore, the ɛ_r of the prepared samples decreased with Sn⁴⁺ substitution, attributed to the lower dielectric polarizability of Sn⁴⁺ cations compared to Ti⁴⁺ cations. Results also indicated a decrease in tan δ with Sn⁴⁺ substitution, resulting from a reduction in octahedral tilting upon partial replacement of Ti⁴⁺ cations with Sn⁴⁺ cations in MgTiO₃. Shielding property characterization revealed that all samples exhibited frequency-selective and tunable shielding capabilities, with tuning achievable through variations in composition or shield thickness. Notably, in the K frequency band, MgO-based MgTiO₃ exhibited superior dielectric properties, with a sample thickness of 2.9 mm achieving a shielding effectiveness (SE) of up to 35.62 dB at 22.30 GHz, effectively suppressing over 99.97% of incoming radiation. Similarly, in the Ka frequency band, MgO-based Mg(Ti_0.95Sn_0.05)O₃ demonstrated remarkable SE, with a sample thickness of 1.8 mm reaching SE of 38.62 dB at 31.60 GHz, attenuating over 99.98% of incoming radiation. These findings suggest potential for frequency-selective and adjustable EMI shielding in next-gen technologies.

Raw materials were etched by nitric acid to release utterly carbon dioxide. An excess of citric acid was then employed as fuel to prime the combustion reaction for the synthesis of Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ (x = 0 (SrBi₂Nb₂O₉), 0.1, and 0.2) compounds. X-ray diffraction, Fourier-transformed infrared, and Raman techniques revealed quite certain that there is a link between dopant amounts and structural changes. One is that the cell volume was smoothly reduced. Second, the bond force constant decreased slightly when the dopant was introduced into the lattice. Even though the SrBi₂Nb₂O₉ compound is not only doped by samarium but also by barium, samarium is the only dopant that affects dielectric and electrical properties. Doping with samarium enhances the dielectric constant at room temperature by reducing the Curie temperature, and it turns ferroelectric normal into relaxor behavior. The results of AC conductivity and electrical modulus laid out that one extreme defect was that a significant amount of cation exchange occurs in Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ samples and a large amount of oxygen vacancies were released. Overlapping large polaron tunneling model (OLPT) mechanisms was the adequate model for these compounds.

Cerium dioxide (CeO₂) finds extensive utility in electro ceramics applications, including solid oxide fuel cells, oxygen sensors, and catalysts. However, Spark Plasma Sintering (SPS) of CeO₂ presents challenges due to the increased mobility of O²⁻ ions in the presence of an electric field, as well as its reactivity with graphite tooling. Traditionally, CeO₂ is sintered in an oxidative environment to prevent it from reducing to CeO_2−δ or Ce₂O₃. Nevertheless, oxidative atmospheres are detrimental to the graphite and steel tooling used in SPS processing. In this study, we investigated CeO₂ SPS in a CO₂ atmosphere and observed slight increase in the relative density (RD) of the as-sintered samples in comparison to those sintered in an Ar atmosphere. The improved densification is attributed to reduced formation of oxygen vacancies in the CO₂ atmosphere. Furthermore, the reaction between CeO₂ and graphite generates CO_x gases, and that reaction can be reversed in a CO₂ atmosphere. In summary, CeO₂ SPS in a CO₂ environment demonstrates superior densification, effectively mitigating the challenges associated with ionic mobility and graphite reactivity.