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We performed B3PW and B3LYP computations for BaTiO3 (BTO), CaTiO3 (CTO), PbTiO3 (PTO), SrTiO3 (STO), BaZrO3 (BZO), CaZrO3 (CZO), PbZrO3 (PZO) and SrZrO3 (SZO) perovskite neutral (001) along with polar (011) as well as (111) surfaces. For the neutral AO- as well as BO2-terminated (001) surfaces, in most cases, all upper-layer atoms relax inwards, although the second-layer atoms shift outwards. On the (001) BO2-terminated surface, the second-layer metal atoms, as a rule, exhibit larger atomic relaxations than the second-layer O atoms. For most ABO3 perovskites, the (001) surface rumpling s is bigger for the AO- than BO2-terminated surfaces. In contrast, the surface energies, for both (001) terminations, are practically identical. Conversely, different (011) surface terminations exhibit quite different surface energies for the O-terminated, A-terminated and BO-terminated surfaces. Our computed ABO3 perovskite (111) surface energies are always significantly larger than the neutral (001) as well as polar (011) surface energies. Our computed ABO3 perovskite bulk B-O chemical bond covalency increases near their neutral (001) and especially polar (011) surfaces.

We performed, for first time, ab initio calculations for the ReO2-terminated ReO3 (001) surface and analyzed systematic trends in the ReO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surfaces using first-principles calculations. According to the ab initio calculation results, all ReO3, SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surface upper-layer atoms relax inwards towards the crystal bulk, all second-layer atoms relax upwards and all third-layer atoms, again, relax inwards. The ReO2-terminated ReO3 and ZrO2-terminated SrZrO3, BaZrO3, PbZrO3 and CaZrO3 (001) surface band gaps at the Γ–Γ point are always reduced in comparison to their bulk band gap values. The Zr–O chemical bond populations in the SrZrO3, BaZrO3, PbZrO3 and CaZrO3 perovskite bulk are always smaller than those near the ZrO2-terminated (001) surfaces. In contrast, the Re–O chemical bond population in the ReO3 bulk (0.212e) is larger than that near the ReO2-terminated ReO3 (001) surface (0.170e). Nevertheless, the Re–O chemical bond population between the Re atom located on the ReO2-terminated ReO3 (001) surface upper layer and the O atom located on the ReO2-terminated ReO3 (001) surface second layer (0.262e) is the largest.

Proton-conducting ceramics (e.g. doped barium zirconates or cerates) are typically mixed ionic-electronic conductors (MIECs). The electronic conduction, typically in the form of positively charged small polarons or electron holes, leads to ‘electronic leakage.’ In an ideal steam-electrolysis cell, one gas-phase H 2 molecule is produced from every two electrons delivered from an external power source. In other words, such ideal behavior achieves 100% faradaic efficiency. However, the electronic flux associated with MIEC membranes contributes to reduced faradaic efficiency. The present paper develops a model that predicts the behavior of faradaic efficiency as a function of electrolysis-cell operating conditions. Although the model framework is more general, the paper focuses on the behavior of a cell based upon a BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3 − δ (BCZYYb) membrane. The study predicts the effects of operating conditions, including temperature, pressure, and gas compositions.

The erosion caused by high-temperature calcium–magnesium–alumina–silicate (CMAS) has emerged as a critical impediment to the advancement of thermal barrier coating (TBC). In this study, a series of high-entropy rare earth zirconates, (La0.2Sm0.2Dy0.2Er0.2Gd0.2)2(Zr1−xCex)2O7 (x = 0, 0.2, 0.4, 0.5) were synthesized through a solid-phase reaction, and their corrosion behavior against CMAS was investigated. Our findings demonstrate that numerous rare earth elements impede element diffusion, facilitate the formation of a compact oxide layer, and effectively hinder CMAS infiltration. Furthermore, rare earth elements with larger ionic radii exhibit enhanced solubility in apatite, whereas those with smaller ionic radii are more readily soluble in ZrO2. In general, the utilization of the high-entropy strategy is an effective approach to significantly improving corrosion resistance against CMAS.

In this paper, we report on the synthesis of BaZrO sub(3) nanostructures by novel bottom-up synthesis methods. Nanocrystals with diameters ranging from 5 to 10 nm are prepared from aqueous or multiple phase precursor solutions. In order to transform the precursor solutions into nanocrystal containing suspensions, both conventional and microwave-assisted solvothermal treatments are used. An additional heat treatment was necessary to obtain crystalline particles starting from the aqueous precursor, while crystalline particles are directly obtained after solvothermal treatment of the multiple phase precursor. The crystallinity and size of the obtained nanoparticles are investigated by means of dynamic light scattering, X-ray diffraction and transmission electron microscopy. We found that the nature of the bases used in the multiple phase precursor have an effect on the particle morphology. In general, the microwave-assisted solvothermal synthesis renders the best prospects towards small particle sizes between 3 and 5 nm in diameter with a narrow size distribution. In addition, the process exhibits higher energy efficiency, resulting in lower reaction times (5 min-2 h) in comparison with the conventional solvothermal treatment (4-24 h).

The article presents the results of a study of the interaction of titanium melt with of zirconates BaZrO 3 and SrZrO 3 , as well as titanate SrTiO 3 under vacuum conditions and in an inert atmosphere at normal pressure. An original titanium heating method was used during the experiments. It eliminated the melt circulation at the interface between the solid and liquid phases. The method was based on resistive electrical heating of a Grade 2 titanium alloy rod or strip pressed into BaZrO 3 , SrZrO 3 and SrTiO 3 powders. Studied the structure, elemental, and phase composition of the products formed during various (up to 300 s) contact of titanium melt with surface zirconates and titaniums. The phase composition was compared with the products obtained by heating compacts from a mixture of titanium powders with BaZrO 3 , SrZrO 3 and SrTiO 3 powders. It was shown based on the results obtained that titanium, upon contact with these ceramic materials dissolves zirconium and oxygen and reduces barium and strontium to a metallic state. Barium and strontium evaporated due to the high vapor pressure at the experimental temperature, and caused the melt to splash or form a vapor layer that reduced the interaction rate of the melt with the ceramic. When a titanium melt interacted with BaZrO 3 and SrZrO 3 intermediate phases were not formed in quantities sufficient for their identification. The Sr 3 Zr 2 O 7 phase was formed in small quantities during heating a mixture of Ti+SrZrO 3 powders. When a titanium melt interacted with SrTiO 3 , a layer of an intermediate phase was formed, similar in composition to TiO 2 . Equations for the chemical reaction of the interaction of titanium with the indicated zirconates and titanate were compiled based on the experimental data obtained. It has been shown that titanium melt weted the surface of BaZrO 3 , SrZrO 3 powders well and poorly weted the surface of SrTiO 3 powder.

This study evaluates the impact of incorporating varying contents (10–40 wt%) and molar concentrations (0.001–1 M) of citric acid solutions, as transient liquid phases in the Cold Sintering Assisted Sintering (CSAS) process of dysprosium zirconate (Dy 2 Zr 2 O 7 ). CSAS processed samples achieved relative densities up to 98% of the theoretical maximum and significantly increased Vickers microhardness by over 2.5 times, compared to the traditional ‘press and fired’ sintering method. The Dy 2 Zr 2 O 7 crystal structure remained consistent with the fluorite-type, with no secondary phases detected. Our findings underscore the benefits of using CSAS to enhance the mechanical strength of Dy 2 Zr 2 O 7 , while reducing the lengthy processing times at very high temperatures typically required for sintering refractory materials such as lanthanide zirconates.

Hydrogen production from water electrolysis is a key enabling energy storage technology for the large-scale deployment of intermittent renewable energy sources. Proton ceramic electrolysers (PCEs) can produce dry pressurized hydrogen directly from steam, avoiding major parts of cost-driving downstream separation and compression. However, the development of PCEs has suffered from limited electrical efficiency due to electronic leakage and poor electrode kinetics. Here, we present the first fully operational BaZrO3-based tubular PCE, with 10 cm2 active area and a hydrogen production rate above 15 Nml min−1. The novel steam anode Ba1−xGd0.8La0.2+xCo2O6−δ exhibits mixed p-type electronic and protonic conduction and low activation energy for water splitting, enabling total polarization resistances below 1 Ω cm2 at 600 °C and Faradaic efficiencies close to 100% at high steam pressures. These tubular PCEs are mechanically robust, tolerate high pressures, allow improved process integration and offer scale-up modularity.Proton ceramic electrolysers can produce hydrogen directly from steam, but their development has suffered from limited electrical efficiency. A fully operational and stable BaZrO3-based tubular electrolyser with high hydrogen production rate is now reported.

Rare-earth zirconates have received attention in recent years due to satisfying the required properties of TBCs application. In this study, three compounds of lanthanum zirconate (LZ), yttrium zirconate (YZ), and lanthanum-yttrium zirconate (LYZ) with a molar ratio of La 3+ /Y 3+  = 1 were prepared through co-precipitation and spark plasma sintering. In LYZ sample, a part of yttria is dissolved in LZ phase and its excess is precipitated as defect fluorite phase. In addition, after the Spark Plasma Sintering (SPS) process, the crystallinity of all three samples increased, and no phase change occurred. Despite using the same parameters in the SPS process, the porosity percentages of LZ, YZ, and LYZ samples was 18.5, 14.8, and 12.7, respectively. Based on the microhardness results, the hardness values of the LZ and YZ samples were close to each other (6.7 ± 0.7 and 7.1 ± 0.5 GPa, respectively), but the LYZ sample showed a higher hardness (8.3 ± 0.4 GPa) due to its better sinterability and solid solution strengthening mechanism. The wear rates of LZ, YZ, and LYZ were 0.05, 0.2, and 2 × 10 −3 mm 3 /N m, respectively. The higher fracture toughness of the LZ sample has prevented further crack propagation during the wear test. Delamination and adhesive were the main wear mechanisms in all samples.

Over the past two decades, lead-free piezoceramics have been developed aiming to replace toxic lead-bearing lead zirconate titanate (PZT). A large number of lead-free piezo systems were explored during this period as evidenced from the huge number of publications. At this juncture, it was felt necessary to publish a review article focusing on material systems and processes delivering high d33 in order to give direction to future research for its further improvement equivalent to or higher than the d33 level delivered by PZT. The important lead-free piezo systems under consideration are: modified barium titanates such as barium calcium titanate zirconate (BCTZ), barium calcium tin titanate (BCSnT), barium calcium hafnium titanate (BCHfT), and potassium sodium niobate (KNN). In this article, an effort has been made to review the high piezoelectric properties achieved on the above lead-free piezo systems explaining the reasons and mechanisms behind high piezo properties and possible future directions of the research for further enhancement of properties.