Journal of Electroceramics最新文献

Potassium sodium niobate (KNN)-based ceramics exhibit electrical (such as ferroelectric) and photoluminescence (PL) properties and have great application potential in the field of multifunctional optoelectronics. To promote its development in the field of optoelectronics, researchers have been making efforts to improve its photoelectric performance, but mainly through experimental approach with little fundamental theoretical calculations. In this paper, the structural, electronic, and optical properties of (K_0.5Na_0.5)NbO₃, K_0.375Na_0.5Er_0.125NbO₃ and K_0.5Na_0.375Er_0.125NbO₃ material were simulated based on first-principles calculations. The calculation of formation energy reveals that Er is more inclined to replace Na than A-site K. The introduction of Er leads to a decrease in the lattice constant of the structure, and the oxygen octahedron relaxes inward, which is beneficial to the enhancement of ferroelectricity. The orbital hybridization of Er-4f and O-2p leads to a narrower band gap and an increase in absorbance and conductivity. The A-site substitution of Er produces a non-uniform chemical bond environment locally, which is beneficial to the improvement of PL performance. These results provide theoretical insights for doping mechanism of the KNN-Er system and show its potential in the field of optoelectronic applications.

Secondary ion mass spectrometry (SIMS) is a sophisticated and powerful analytical technique to characterise the surface and sub-surface of materials. It has been widely used in materials science due to its trace level sensitivity to the full range of elements and isotopes, capability of profiling from surface to bulk, and various modes to provide information from the mass spectrum to 2D and 3D elemental distribution. In this article, we will discuss the working principles of SIMS, instrumentation information, issues related to measurements and data analysis with some case studies as well as the possible pitfalls. It will be by no means exhaustive for SIMS analysis but the aim of this article is to lower the boundaries for students and researchers who are going to perform their first SIMS analyses. The examples will be focused on solid state materials for energy applications only, albeit SIMS has been widely used for the surface analysis on all kinds of materials.

The influence of TiO₂ on the crystal phase, microstructure, thermal conductivity, and microwave dielectric properties of Mg-Ti-O-based ceramics during sintering are explored. XRD analysis reveals that doped TiO₂ completely reacts with Mg₂TiO₄ to generate MgTiO₃, and (1-y)Mg₂TiO₄ + yMgTiO₃ ceramics are obtained. The undoped TiO₂ samples exhibit an excessively large grain size with an uneven grain size distribution and numerous pores. The reaction between TiO₂ and Mg₂TiO₄ effectively reduces the grain size of Mg₂TiO₄ to a reasonable range, thereby facilitating the mitigation of internal defects within grains. Additionally, the formation of MgTiO₃ results in a microstructure characterized by two phases with staggered distribution and mutual inhibition. This phenomenon aids in controlling the growth and arrangement of grains, ultimately filling pores and enhancing ceramic density. A reasonable grain size and regular arrangement are advantageous for improving the thermal and dielectric performance of ceramics compared to excessively larger grains and uneven distribution. Mg-Ti-O-based ceramics contribute to an enhancement in thermal conductivity to 10.1 W/(m·K) and in Q×f value to 143,046 GHz.

In this research, eco-friendly (Bi_0.49−xBa_xLa_0.01Na_0.40K_0.10)TiO₃ or BiBa_xLNKT ceramics (where x = 0–0.15 mol fraction) were fabricated by solid-state mixed oxide technique, and their phase evolution, physical, microstructure, mechanical, dielectric, piezoelectric, ferroelectric, energy storage density, and energy harvesting properties have been systematically investigated. All ceramics exhibited a single perovskite structure. With increasing Ba content, a phase transition from mixed rhombohedral-tetragonal to be more tetragonal-rich phase was observed. The addition of Ba inhibited grain growth and resulted in densification, mechanical, and dielectric improvement. The maximum values of HV (6.01 GPa), HK (5.78 GPa), E (78 GPa), K_IC (1.38 MPa.m^1/2), ε_r (1604), and tan δ (0.0504) were observed for the x = 0.15 ceramic. The x = 0.15 ceramic also showed excellent piezoelectric performances (d₃₃ = 248 pC/N, g₃₃ = 17.46 × 10⁻³ Vm/N, and k_p = 49%) and good off-resonance figure of merit (FoM) for energy harvesting (4.33 pm²/N). Moreover, after the introduction of Ba content, the ferroelectric long-range order is broken, which contributes to energy storage density improvement. Especially, the x = 0.05 ceramic achieved excellent recoverable energy storage density (W_rec = 1.31 J/cm³) and good energy storage efficiency (η = 96.18%) at 150 °C under driving electric fields (E) of 75 kV/cm. All results indicated that we can efficiently fabricate an environment-friendly (Bi_0.49−xBa_xLa_0.01Na_0.40K_0.10)TiO₃ system with good reliability for energy harvesting and high-temperature energy storage capacity applications.

Nickel manganese oxide (NiMn₂O₄) is a versatile mixed metal oxide with a range of potential applications across various fields. It belongs to the spinel structure family, characterized by a cubic crystal structure with specifically arranged cationic and anionic lattice sites. Nickel manganite is a ceramic material that can be produced in miniaturized form using various fabrication processes. This article aims to explore the suitability of this material for various applications, particularly in NTC thermistors. Thermistor materials are widely used in sensing applications in science, engineering, and technology. They are applied in time delay circuits, device protection, voltage regulation, speech volume control, testing equipment for ultra-high-frequency power, and detecting very small amounts of radiant energy. This review seeks to provide valuable insights into the synthesis strategies for nickel manganite, guiding researchers and experts by offering useful information on the appropriate methods for fabricating nickel manganite to meet the specific requirements of NTC thermistors in sensing applications. The article discusses in detail the various synthesis techniques of nickel manganite and how these techniques influence its structure and other properties.

This study presents the synthesis of Au and Fe₂O₃ nanoparticles (NPs) embedded on SnO₂ nanowires (NWs) using a vapor–liquid–solid (VLS) and hydrothermal method. The resulting Au@Fe₂O₃@SnO₂ NW composites demonstrated a remarkable response of 133.05 at an optimal operating temperature of 225 °C when exposed to 20 ppm of acetone gas, significantly outperforming pure SnO₂ NWs by a factor of 23. These composites also exhibited excellent selectivity and long-term stability in acetone gas detection. A thorough investigation into the sensor’s operational mechanism revealed that the interactions between acetone molecules and adsorbed oxygen, along with electron transfer processes, result in changes in sensor resistance. The superior gas-sensing properties are primarily attributed to the well-defined one-dimensional (1D) microstructure, featuring closely connected n–n heterojunctions of SnO₂ and Fe₂O₃, which provide a large specific surface area with numerous active sites. These sites facilitate the reaction between acetone molecules and oxygen ions on the surface, enhanced by the catalytic effect of Au. This work underscores the potential of this fabrication method for developing gas sensors capable of detecting acetone at low ppm levels in a 225 °C environment.

Oxy-apatite lanthanum silicates with general formula La₁₀Si_5.9M_0.1O_27±δ (M = Cr³⁺, Mn⁴⁺, Fe³⁺, Mo⁶⁺, W⁶⁺; 0.05 ≤ δ ≤ 0.1, coded LaSiMO) were obtained by gel-combustion and they were characterized through electrochemical impedance spectroscopy. The XRD patterns show that all samples adopt apatite structure and crystallize in the hexagonal space group P-3(147) with crystallite sizes ranging from 86 nm to 103 nm. The dopant cations were accommodated at Si position with the highest occupancy factor at O6 sites (responsible in conduction) for LaSiCrO and LaSiFeO apatites. Fe and Cr doped samples contain pure apatite phase while those doped with Mn, Mo, W contain La₂SiO₅ as secondary phase which act as insulator in conduction process. Based on EPR and ICP-OES investigations we found that Mn, Mo, W cations present multiple oxidation states in the apatite lattice and a lower incorporation degree in comparison with Fe and Cr cations. Local distortions are present in Fe and Cr doped apatite lattices which explains the higher ionic conductivity of these samples. At 500^oC, the ionic conductivities, range between 1.15·10^− 4 and 3.56·10^− 4 S·cm^− 1 for samples sintered at 1400^oC, values that are higher than un-doped apatite (6.46·10^− 5 S·cm^− 1). Due to the highest ionic conductivity among the samples, LaSiCrO was additionally sintered at 1500^oC and 1600^oC in order to investigate the role of temperature on ionic conduction process. The relative density of LaSiCrO was improved from 89.03 to 93.06% and the ionic conductivity reach 0.28·10^− 2 S·cm^− 1, at 600^oC. The results of this study show that apatites doped with Cr and Fe may be used as electrolytes in SOFCs.

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.