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Rare earth hafnates and zirconates are candidate materials for thermal and environmental barrier coatings (T/EBC) to protect gas turbine engine components from various environmental threats, including molten silicates derived from ingested mineral debris. This article examines the reactions of Gd2Hf2O7 (GHO) and Gd2Zr2O7 (GZO) to exemplary acidic and basic silicate melts. Exposure experiments at 1400°C reveal that both materials react to form mixed layers of apatite and fluorite. These layers largely hinder melt penetration of grain boundaries in GZO for exposures up to 4 h. However, extensive intergranular melt penetration occurs into GHO below the reaction layer within 1 h for the acidic melt and within 4 h for the basic melt. Shorter exposures (1–5 min) of Gd‐lean versions of the two compounds, viz. Gd0.2Hf0.8O1.9 and Gd0.2Zr0.8O1.9, are used to probe differences in the dissolution and diffusion rates. While both oxides form fluorite, the HfO2‐based one reacts more slowly than that based on ZrO2. Analysis of composition profiles across the solid/melt boundary reveals that Hf4+ diffuses more slowly than Zr4+ and that the hafnate dissolves more slowly than the zirconate; in both cases dissolution is diffusion‐controlled. The implications for the efficacy of reactive crystallization as a silicate mitigation strategy are discussed. [ABSTRACT FROM AUTHOR]

Background Ceramic materials are currently in wide demand in various fields of medicine. Zirconium ceramics demonstrate exceptional mechanical properties and biocompatibility and do not cause cytotoxic effects or allergic reactions in surrounding tissues. The objective was to present an analysis of current literature data on the use of zirconium ceramics as a bone replacement material in traumatology and orthopaedics. Materials and methods The search for publications was conducted using the databases of Scopus, PubMed and the electronic scientific library eLIBRARY in the Russian and English languages using the keywords: bioceramics, bone, bone defect, zirconate, zirconium ceramics, bone tissue engineering, implant, scaffold, augment, biointegration, bioactivity. Depth of search for scientific papers was from 2000 to 2023. Results and discussion Zirconium dioxide is the main ceramic bioinert material. The study presents the characteristics of ZrO2 as a bone replacement material and its comparison with titanium implants. Data are presented on various strategies for improving zirconium bioceramics: improving the surface of the material by physical and chemical methods, obtaining volumetric porosity, including using additive technologies, creating composite materials, and developing bioactive coatings. New methods of creating zirconium ceramics compatible with living tissues containing bioactive ions that promote both osseointegration and bone tissue regeneration have been actively studied. Conclusions Zirconium dioxide ceramics appear to be a promising alternative to titanium implants in terms of mechanical strength, biological functionality, chemical stability, osseointegration, and antibacterial properties. Future experimental and clinical studies will further improve zirconium ceramics.

Multicomponent oxides have received significant recent attention due to their potential for improved property tunability. In simple structures, compositionally complex oxides can be stabilized by increased configurational entropy and are sometimes called "high entropy" ceramics. In phases with multiple cation sublattices or complex stoichiometries, it is more difficult to achieve high configurational entropy. However, there is limited knowledge about the factors influencing stability and solubility limits in many systems. This study investigated the limits on the stability of rare earth (RE) aluminates containing mixtures of RE cations including Gd, La, Nd, Yb, and Y in cases where (i) a fixed RE:Al ratio attempts to constrain the material into a single‐phase aluminate or (ii) a two‐phase aluminate, and in equilibrium with RE zirconates that readily dissolve multiple RE3+. The results show that it is difficult to form single‐phase, equimolar mixed‐RE aluminates encompassing a range of RE3+ sizes. Instead, the RE3+ selectively partition into specific phases based on RE‐size trends in the constituent binary systems. The results are discussed in terms of the phase stability and cation partition trends and potential applications. [ABSTRACT FROM AUTHOR]

In response of swift heavy ion (100 MeV I9+) irradiation, the irradiation‐induced disordering in nonstoichiometric pyrochlore composition (Nd1.8Zr2.2O7.1) was compared to that of stoichiometric composition Nd2Zr2O7. Both compositions were prepared through auto gel‐combustion followed by sintering under the identical conditions. Systematic analysis of the compositions before and after irradiation was performed with X‐ray diffraction (XRD), Raman spectroscopy, and plane‐view high‐resolution transmission electron microscopy (HRTEM) techniques. Irradiation caused pyrochlore to amorphous phase transformation was observed in both compositions except the slower rate of amorphization in Nd1.8Zr2.2O7.1. The amorphization was achieved as a consequence of isolated disordered track overlapping at higher ion fluence with the estimated track diameter 2.73 ± 0.05 and 3.46 ± 0.30 nm for Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively, employing the framework of single‐ion impact model to XRD results. HRTEM micrographs also revealed the less prevalence of irradiation‐induced amorphization in Nd1.8Zr2.2O7.1 with the observed irradiation‐induced modified track region composed of defect‐rich pyrochlore structure, anion‐deficient fluorite structure, and amorphous domains; with the diameter of 3.0 ± 1.0 nm and 5.0 ± 1.0 nm in Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively. The preexisting anion‐deficient fluorite structure in Nd1.8Zr2.2O7.1 helps in its epitaxial growth as recovered structure from melted ion track during irradiation‐induced rapid cooling. [ABSTRACT FROM AUTHOR]

Thermal and environmental barrier coatings must be robust against attack by calcium magnesium aluminosilicate (CMAS, or CMFAS with iron) deposits, and coatings that produce thin, uniform reaction layers are desirable. The reactions of four multiphase coating compositions in the AlO 1.5 –REO 1.5 –ZrO 2 systems (RE = Gd or Y) with three model CMFAS deposits were studied. Following CMFAS exposure for 1 h at 1400°C, some samples exhibited thin, uniform CMFAS reaction product layers, while others were less uniform with pockets of deep reactions. Coating materials with higher AlO 1.5 content produced uniform reaction layers, while the most SiO 2 -rich CMFAS was most likely to produce a non-uniform response. Apatite was formed in all cases, while the Y was more likely than Gd to form aluminosilicate garnet and cuspidine reaction products. The results are discussed in terms of implications for CMFAS-resistant T/EBC design. [ABSTRACT FROM AUTHOR]

Zirconate fibrous membranes show promising applications in high thermal insulating areas for the high melting point, low thermal conductivity and good phase stability. To satisfy the high-temperature mechanical demands, the microstructure of zirconate fibers needs further modification to accommodate high-temperature stability. In consideration of the slow ion diffusion rate and enhanced stability of solid solution, Ca x Sr 1- x ZrO 3 fibrous membranes were electrospun with molar ratio of Ca/Sr varied from 0.9 to 0.5 for the present work. The effects of strontium precursor on the pyrolysis process, phase formation and microstructure evolution were fully characterized. Modified microstructures with smaller grain size and narrow particle size distribution were achieved. Furthermore, the NIR reflectivity, thermal conductivity, and high-temperature stability were also presented. The special expansion character of fibrous membrane at high temperature would make it promising candidate to compensate the shrinkage of other oxide fibrous membrane. [ABSTRACT FROM AUTHOR]

The challenge in synthesizing high-entropy ceramic (HEC) nanopowders is to suppress severe grain coarsening and particle agglomeration, which occur at elevated temperatures. This challenge could be addressed by the polyacrylamide gel method. In this work, single-phase high-entropy (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 and (La0.2Nd0.2Y0.2Eu0.2Gd0.2)2Zr2O7 nanopowders without agglomeration were successfully synthesized using the polyacrylamide gel method for the first time. The results showed that phase composition, particle size, and agglomeration degree of the nanopowders were greatly influenced by the molar ratio of acrylamide (AM)/Zr and calcination temperature. These as-synthesized high-entropy zirconate (HEZ) nanopowders could be sintered into fully dense ceramics at 1500 ℃ for 2 h. These HEZ nanopowders showed a phase transformation from a defect-fluorite phase to a pyrochlore phase with the increase of sintering temperature. Additionally, two-step sintering of these nanopowders was conducted, and the HEZ ceramics with fine grains were prepared. The polyacrylamide gel method is simple and easily operated, which is a facile approach of producing the HEC nanopowders with excellent sinterability.

Preparation of Gd 2 Zr 2 O 7 nanoceramics using a simple and low energy-consuming approach is significant for their wide range of applications. In this work, flash sintering (FS) and two-step flash sintering (TSFS) were first utilized to prepare Gd 2 Zr 2 O 7 nanoceramics. The effects of electric field intensity and current limit on the densification and grain growth were investigated. The grain size was decreased with the increase of electric field intensity. Meanwhile, both grain size and density were increased with the increase of current limit. The Gd 2 Zr 2 O 7 nanoceramics with an average grain size of 98 nm and a relative density of 92.8% were prepared by FS. By contrast, the Gd 2 Zr 2 O 7 nanoceramics with the higher relative densities of 96.3–97.5% and the smaller average grain sizes of 85–90 nm were prepared by TSFS. Compared to FS, TSFS can achieve suppressed grain growth and fast densification. The as-prepared Gd 2 Zr 2 O 7 nanoceramics showed excellent hardness and fracture toughness. The sample breakage caused by current localization can be avoided by controlling the current ramp after the occurrence of the flash event. [ABSTRACT FROM AUTHOR]

Short-range order is a new strengthening effect that can significantly affect the mechanical properties of high-entropy materials. Furthermore, simulation results show that this strengthening effect at a quasi-atomic scale can suppress the grain size softening, leading to the disappearance of inverse Hall-Petch behavior in nanocrystalline high-entropy materials. In this work, the evident inverse Hall-Petch behavior is confirmed in the translucent nanocrystalline high-entropy ceramic (HEC) with an average grain size below 10 nm, fabricated by a high-pressure low-temperature sintering technique. Besides, the as-obtained nanocrystalline HEC also shows an improving fracture toughness compared with the corresponding coarse-crystalline HEC. [ABSTRACT FROM AUTHOR]

Fabrication of transparent or pore‐free oxide ceramics usually requires sintering in a vacuum or reducing atmosphere. In the present paper, a near‐infrared transparent Dy2Zr2O7 ceramic was prepared by ordinary pressureless sintering under the air atmosphere, with a controlled pre‐calcining of raw powders process. The key point of the process is to control the content of the phases by pre‐calcination of the starting mixture of ZrO2 and Dy2O3 powders. The influence of pre‐calcining temperature on the content of phases, the particle sizes, on the sinterability of the mixture of Dy2O3 and ZrO2 powders has been investigated. It was found that when the pre‐calcination was conducted at 1200°C for 2 h, the powder contains 4 mol% Dy2Zr2O7, 18 mol% m‐ZrO2, 30 mol% Dy2O3, and about 50 mol% t/c‐ZrO2 which is beneficial for the sintering of pore‐free Dy2Zr2O7 ceramics. The mechanism is discussed in the paper. The transparency of the sintered Dy2Zr2O7 ceramic was measured, and their transmittance is about 63% at 1450 nm and 73% at 1900 nm. This work provides a simple and convenient way to prepare the near‐infrared transparency ceramic without special sintering facilities. [ABSTRACT FROM AUTHOR]

Here we report a new high‐Q × f and temperature‐stable oxyfluoride microwave dielectric ceramic system of Li2+xZrO3Fx (0 ≤ x ≤ 1.25) sintered at low temperatures (i.e., ≤950°C). The sintering characteristics, phase assemblage, microstructures, and microwave dielectric properties (MDPs) of the Li2+xZrO3Fx specimens were studied. The chemical bond theory calculations were employed to analyze the compositional dependence of the MDPs in the Li2+xZrO3Fx ceramic system. The optimal MDPs of εr = 15.8, Q × f = 65 100 GHz, and τf = 1.2 ppm/°C were achieved in the sample with x = 1. Besides, the ceramic samples exhibited high chemical compatibility with Ag electrodes. Therefore, the novel ceramic system of Li2+xZrO3Fx is confirmed to be a promising candidate as a low‐temperature co‐fired ceramic material. [ABSTRACT FROM AUTHOR]

As the demand for higher operating temperatures in gas turbine engines, low thermal conductivity thermal/environmental barrier coatings (T/EBCs) systems are urgently needed to protect the structural components of silicon carbide ceramic matrix composites (SiC CMCs). In this paper, several T/EBCs systems with zirconate as the top layer were prepared by air plasma spraying (APS) on environmental barrier coatings (EBCs) systems, and thermal cycling tests were carried out at 1400 °C in a 90 % H 2 O-balanced O 2 water vapor atmosphere. When there were no transition layers, the zirconate top layer produced many horizontal and vertical cracks under severe thermal mismatch stress. When the transition layers existed, the thermal mismatch stress was obviously relieved and the horizontal cracks basically disappeared. The morphology of the vertical cracks in the zirconate top layer varied with the different transition layers, and no obvious cracks were found in both the Yb 2 Si 2 O 7 or mullite transition layers, indicating that they are highly resistant to crack extension. For the bonding layer, the addition of HfO 2 particles into the Si layer significantly suppressed crack propagation. These findings may contribute to laying the foundation for the material and structural design of transition layers in long-life T/EBCs systems. • The APS-prepared (Gd 0.9 Yb 0.1) 2 Zr 2 O 7 layer is suitable for use with the Yb 2 SiO 5 transition layer. • The addition of HfO 2 particles to the Si bonding layer improves the crack extension resistance. • Two optimized multilayer T/EBCs coating systems are suitable for applied on SiC substrates in this study. [ABSTRACT FROM AUTHOR]

The reaction of dry and pulverized rice husk with alkaline CS2 followed by treatment of the resulting xanthate derivative with zirconyloxychloride at room temperature led to functionalization of the xanthated biomass with sodium zirconate grouping. The as-prepared sodium salt of the rice-husk xanthatozirconate was characterized physicochemically and found to be an efficient, robust, and recyclable catalyst for the three-component synthesis of some spiro[4H-pyran-4,3′-indoline]s in water. [ABSTRACT FROM AUTHOR]

In the future, when fossil fuels are exhausted, alternative energy sources will be essential for everyday needs. Hydrogen-based energy can play a vital role in this aspect. This energy is green, clean, and renewable. Electrochemical hydrogen devices have been used extensively in nuclear power plants to manage hydrogen-based renewable fuel. Doped zirconate materials are commonly used as an electrolyte in these electrochemical devices. These materials have excellent physical stability and high proton transport numbers, which make them suitable for multiple applications. Doping enhances the physical and electronic properties of zirconate materials and makes them ideal for practical applications. This review highlights the applications of zirconate-based proton-conducting materials in electrochemical cells, particularly in tritium monitors, tritium recovery, hydrogen sensors, and hydrogen pump systems. The central section of this review summarizes recent investigations and provides a comprehensive insight into the various doping schemes, experimental setup, instrumentation, optimum operating conditions, morphology, composition, and performance of zirconate electrolyte materials. In addition, different challenges that are hindering zirconate materials from achieving their full potential in electrochemical hydrogen devices are discussed. Finally, this paper lays out a few pathways for aspirants who wish to undertake research in this field. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells (PCFCs) using BaZr0.8−xCexY0.2O3−δ (BZCY) as electrolyte materials have attracted widespread attention because of their high performance at reduced temperature. However, there are few systematic studies on both the performance and stability of BZCY materials. In this paper, we report our work on the electrochemical performance and chemical stability of BaZr0.8−xCexY0.2O3−δ (x = 0, 0.1, 0.3, 0.5, and 0.7) series. The results show that electronic hole conductivity decreases with increasing Ce4+ content, especially at high temperature. In addition, H2 atmosphere reduces the conductive activation energy of BZCY. On the contrary, air atmosphere causes serious electronic leakage. These effects are also reflected in the operation of PCFCs, that is, the higher the Ce4+ content, the higher the open‐circuit voltage and output power density. However, low Ce4+ content may stabilize the materials in CO2 atmosphere. At 700°C, an anode‐supported PCFC based on BaZr0.1Ce0.7Y0.2O3−δ electrolyte, using humid H2 fuel, gives a peak power density of 1.0 W cm−2. At 600°C, BaZr0.8Y0.2O3−δ and BaZr0.7Ce0.1Y0.2O3−δ show a good stability in CO2‐containing atmosphere. [ABSTRACT FROM AUTHOR]

A series of compositionally complex A 2 Zr 2 O 7 nanocrystalline ceramics were successfully prepared using sol-gel and co-precipitation methods. The resultant ceramics possess a cubic defect fluorite structure, with the sol-gel method yielding an average grain size of approximately 50–70 nm, while the co-precipitation method result in an average grain size of about 40–60 nm. Leaching tests revealed that the smaller grain sizes are correlated with higher leaching rates. Furthermore, for ceramics with similar grain sizes, those with higher entropy values exhibited higher leaching rates. The increase in grain boundaries was found to reduce the leaching performance of the rare earth zirconate ceramics, and this effect became more pronounced with increasing entropy. This work provides insights into the selection of entropy values and grain sizes for the high-level radioactive waste matrices, which can be considered as a potential substrate for the simultaneous immobilization of multiple radionuclides. [ABSTRACT FROM AUTHOR]

Uranium-bearing radioactive wastes generated from the nuclear fuel cycle and the nuclear medicine sector require conditioning to form stable waste forms for long-term geological disposal. Various candidate ceramic and glass-ceramic composite waste forms designed for the incorporation of tetravalent uranium (U(IV)) have been developed largely based on the general observation that the oxidative dissolution of primary U(IV) minerals controls uranium migration in the geological environment. As such, waste forms must be processed under reducing conditions to maintain U(IV) and often with addition of metal powders to control the reducing environment, significantly increasing the processing cost. In addition, these U(IV) waste forms often require extensive chemical durability testing to see how U(IV) oxidation to U(VI) would impact U releases. Based on numerous natural analogue and laboratory studies, some U(VI) minerals and synthetic phases are found to be chemically durable, making them candidate U(VI) waste forms. This article is not intended to provide a comprehensive review rather serve as a perspective focusing on the current advances and future trend of the U(VI) waste forms for the encapsulation of uranium-bearing nuclear wastes, with some highlighted cases and analysis. Technical challenges and perspectives are provided to identify the knowledge gaps and opportunities for future research. Current progress on candidate hexavalent uranium waste forms has been assessed. Challenges and perspectives are given to identify the knowledge gaps for future research. [Display omitted] • Progress and status on candidate hexavalent uranium waste forms for nuclear waste management are assessed. • Current advances on uranyl silicates, titanates, zirconates, phosphates, vanadates and molybdates are briefly reviewed. • Selected uranyl minerals and synthetic phases as potential hexavalent uranium waste forms are discussed. • Technical challenges and perspectives are given to identify the knowledge gaps for potential future research. [ABSTRACT FROM AUTHOR]

The impact of calcium–magnesium–alumino‐silicate (CMAS) degradation is a critical factor for development of new thermal and environmental barrier coatings. Several methods of preventing damage have been explored in the literature, with formation of an infiltration inhibiting reaction layer generally given the most attention. Gd2Zr2O7 (GZO) exemplifies this reaction with the rapid precipitation of apatite when in contact with CMAS. The present study compares the CMAS behavior of GZO to an alternative thermal barrier coating (TBC) material, GdAlO3 (GAP), which possesses high temperature phase stability through its melting point as well as a significantly higher toughness compared with GZO. The UCSB laboratory CMAS (35CaO–10MgO–7Al2O3–48SiO2) was utilized to explore equilibrium behavior with 50:50 mol% TBC:CMAS ratios at 1200, 1300, and 1400°C for various times. In addition, 8 and 35 mg/cm2 CMAS surface exposures were performed at 1425°C on dense pellets of each material to evaluate the infiltration and reaction in a more dynamic test. In the equilibrium tests, it was found that GAP appears to dissolve slower than GZO while producing an equivalent or higher amount of pore blocking apatite. In addition, GAP induces the intrinsic crystallization of the CMAS into a gehlenite phase, due in part to the participation of the Al2O3 from GAP. In surface exposures, GAP experienced a substantially thinner reaction zone compared with GZO after 10 h (87 ± 10 vs. 138 ± 4 μm) and a lack of strong sensitivity to CMAS loading when tested at 35 mg/cm2 after 10 h (85 ± 13 versus 246 ± 10 μm). The smaller reaction zone, loading agnostic behavior, and intrinsic crystallization of the glass suggest this material warrants further evaluation as a potential CMAS barrier and inclusion into composite TBCs. [ABSTRACT FROM AUTHOR]

Phase formations and dielectric properties of lead free barium titanate bismuth zinc zirconate, BaTiO3-Bi(Zn0.5Zr0.5)O3 (BT-BZZ), were comparatively investigated between two different synthesis routes, solid state reaction and salt flux assistance methods. The perovskite (1-x)BT-(x)BZZ ceramics, where x = 0.02, 0.05 and 0.10, were synthesized by using reagent grade oxides and the NaCl salt was used as a surface active agent to lower the calcination temperature. Phase formations were examined by X-ray diffraction technique (XRD). It was found that the solid solutions of (1-x)BT-(x)BZZ can be obtained with lower temperature at least 200 °C via salt flux assistance method. The NaCl salt addition could result in single phase of perovskite structure at every compositions with the calcination temperature as low as 800 °C. Dielectric measurements revealed that the Curie temperature (Tc) shifted to lower temperature with increase of BZZ concentration. Moreover, the dielectric behavior transformed to diffuse phase transition when x = 0.1. The samples prepared via salt flux assistance method exhibited smaller grain size which were revealed by scanning electron microscope. In addition, P-E hysteresis measurements illustrated the higher high E-field dielectric constant with the narrower P-E loop when the salt flux was applied. [ABSTRACT FROM AUTHOR]

BaZrO 3 -based materials doped with a trivalent cation have excellent chemical stability and relatively high proton conductivity which makes them potential proton conducting oxide materials for various electrochemical device applications such as hydrogen processing, high-temperature electrolysis, and solid electrolyte in fuel cells. However, BaZrO 3 showed poor sinterability, requiring high sintering temperatures (1700–2100 °C) with longtime sintering (20–100 h) to achieve the desired microstructure and grain growth. This sintering problem can be solved by slightly doping BaZrO 3 with a sintering aid element. Therefore, in this study, two different zirconate proton conductors: BaZr 0·9 Y 0·1 O 3-α (BZY) and BaZr 0·955 Y 0·03 Co 0·015 O 3-α (BZYC) were sintered in an air atmosphere and an oxygen atmosphere for 20 h in the temperature range of 1500–1640 °C. The sinterability was evaluated by analyzing the XRD diffraction patterns, lattice constant, lattice strain, crystallite size, relative density, open porosity, closed porosity, surface morphology, grain size, and grain boundary distribution, using the XRD, SEM, EDX, and Archimedes density measurement methods. It is concluded that in an oxygen atmosphere, sintering aid Co not only improves the relative density but also produces highly dense fine particles with clear grain boundaries which are promising for electrochemical hydrogen device applications. [ABSTRACT FROM AUTHOR]

In the future, when fossil fuels are exhausted, alternative energy sources will be essential for everyday needs. Hydrogen-based energy can play a vital role in this aspect. This energy is green, clean, and renewable. Electrochemical hydrogen devices have been used extensively in nuclear power plants to manage hydrogen-based renewable fuel. Doped zirconate materials are commonly used as an electrolyte in these electrochemical devices. These materials have excellent physical stability and high proton transport numbers, which make them suitable for multiple applications. Doping enhances the physical and electronic properties of zirconate materials and makes them ideal for practical applications. This review highlights the applications of zirconate-based proton-conducting materials in electrochemical cells, particularly in tritium monitors, tritium recovery, hydrogen sensors, and hydrogen pump systems. The central section of this review summarizes recent investigations and provides a comprehensive insight into the various doping schemes, experimental setup, instrumentation, optimum operating conditions, morphology, composition, and performance of zirconate electrolyte materials. In addition, different challenges that are hindering zirconate materials from achieving their full potential in electrochemical hydrogen devices are discussed. Finally, this paper lays out a few pathways for aspirants who wish to undertake research in this field.

Research on zircon processing technology has been continued to follow industrial market needed. Treatment of sodium zirconate with leaching process using hydrochloric acid as solvent has been conducted. The aim of the study is to evaluate the effect of grain size, temperature, and speed of stirring on the extracted zircon. The research starting with introduced the solvent (chloride acid 4 N) into the reactor, then heated while stirring. The feed with a certain grain size was introduced into the reactor. The temperature and stirring conditions were kept steady. Once the operating conditions are reached, the process is stopped and then filtered. The results with XRF analysis showed that the optimum process conditions were achieved on 90 μm grain size, the temperature of 80 oC, and stirring speed of 200 rpm. The amount of zircon that taken out were 84.50 % on this conditions.

Three kinds of Gd 2 Zr 2 O 7 /ZrO 2 (GZC) composite fibers with different proportions of Gd 2 Zr 2 O 7 were prepared by electrospinning method through changing the amount of Gd3+ in precursor solutions. The thermal decomposition, crystallization process, high temperature stability and heat-conducting properties of GZC fibers were fully characterized. The results showed that there were three crystalline phases, tetragonal phase ZrO 2 , cubic phase ZrO 2 and defect fluorite phase Gd 2 Zr 2 O 7 in all the GZC fibers. The content of Gd 2 Zr 2 O 7 increased gradually with the increase of Gd3+ in precursor solutions which led to the gradual slowing down of grain growth rate, the decrease of thermal conductivity and the increase of high temperature stability of the obtained composite fibers. The thermal conductivities of all the GZC fiber sheets were lower than that of 7YSZ fiber sheet. The sheets of all the GZC fibers could keep the high temperature stability up to 1300 °C. [ABSTRACT FROM AUTHOR]

Multicomponent oxides with pyrochlore structure (A 2 Zr 2 O 6 O') containing up to 7 different cations with equiatomic amounts have been successfully synthesized, which broadens pyrochlore solid solutions to high entropy pyrochlore oxides. XRD and Raman results indicate that all compositions possessed single-phase pyrochlore structure and the HAADF-STEM images with corresponding EDS mapping demonstrate that all cations were randomly and homogeneously distributed. This new class of high-entropy pyrochlore oxides may open a new research direction in pyrochlore-based materials. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the phase composition, structural properties, and applicability of perovskite-like ceramics of the LiZrBaO x type obtained by solid-phase synthesis. According to the data of X-ray phase analysis, mapping, and TEM images, it was established that the ceramic structure consists of core-shell particles where the ZrO 2 phase acts as the core, and the ZrBa 2 O 4 and Zr 2 Li 6 O 7 phases are a double shell, one of which is the disordered Zr 2 Li 6 O 7 shell. The presence of three phases in the structure leads to a sufficiently strong distortion of the crystalline structure, as well as its deformation. In the course of the research, the prospects of using ceramics based on LiZrBaO x as the basis for the cathode materials of lithium-ion batteries were established. [ABSTRACT FROM AUTHOR]

Gd 2 Zr 2 O 7 /ZrO 2 (GZC) composite fibers were prepared by electro-spinning method. The XRD, XPS and Raman results showed that there were three crystalline phases, tetragonal phase ZrO 2 , cubic phase ZrO 2 and defect fluorite phase Gd 2 Zr 2 O 7 in GZC composite fibers. GZC fibers remained an intact fiber texture up to 1400 °C according to SEM photographs. The thermal conductivity of GZC fibers was between 0.173 W/(m·K) at 400 °C and 0.309 W/(m·K) at 800 °C, which was lower than that of 7YSZ under the same experimental conditions. The fiber sheet with density about 3.5 g/cm3 has thermal shrinkage less than 3% at 1400 °C. Hence, GZC fibers could be used as refractories for heat protection. [ABSTRACT FROM AUTHOR]

Abstract La-Ce-Gd titanate-zirconate pyrochlore-based ceramics was synthesized at the lab-scale inductive melting unit with a 56 mm inner diameter cold crucible. Batch feeding rate and melting ratio were 3 kg/h and 3 kW h/kg respectively. The ceramics is composed of 85–90 vol% zoned grains of the pyrochlore structure phase, the sample has excellent chemical durability in hot water and may be considered as a promising matrix for actinide – rare earth fraction of high level waste. [ABSTRACT FROM AUTHOR]

In the ZrIV complex anion of the title complex salt, [(C4H9)HNC(C6H5)NH2]2[ZrCl6]·2CH2Cl2, the ZrIV cation, located on an inversion centre, is coordinated by six Cl− anions in a distorted octahedral geometry with Zr—Cl distances in the range 2.433 (2)–2.4687 (19) Å; in the amidinium cation, the dihedral angle between the aromatic ring and [NCN] plane is 43.3 (4)°. In the crystal, the amidinium cations and [ZrCl6]2− anions are linked by N—H...Cl hydrogen bonds, forming a two-dimensional network extending along the b axis; two dichloromethane solvent molecules are linked by a pair of weak C—H...Cl hydrogen bonds, forming a centrosymmetric [CHCl]2 six-membered ring.

This paper reports the enhanced photoluminescence from Eu 3+ , A + (Li + , Na + , K + ) co-doped CaZrO 3 phosphors synthesized through solid state reaction method. The X-ray diffraction (XRD) measurement reveals the orthorhombic phase of CaZrO 3 crystal. The scanning electron micrographs (SEM) show that the shape of the particle is converted from polyhedron to cubic on co-doping of alkali ions. All the phosphors emit intense red emission at 613 nm corresponding to 5 D 0 → 7 F 2 transition of Eu 3+ ion under the excitation with 266, 280, 355 and 395 nm wavelengths. The alkali ions enhance the emission intensity of Eu 3+ : CaZrO 3 phosphor due to increase in the asymmetry in the crystal field and charge compensation. The optical band gap of Eu 3+ : CaZrO 3 phosphor decreases and the lifetime of 5 D 0 level of Eu 3+ ion increases in the presence of alkali ions. This material can be a potential red emitting phosphor for UV-based white LED and other display devices. [ABSTRACT FROM AUTHOR]

Understanding the strain from chemical expansion of proton-conducting ceramics is crucial to prevent their failure under operating conditions. BZY10 (BaZr0.9Y0.1O3−δ) and BZCY72 (BaZr0.7Ce0.2Y0.1O3−δ) were studied using high-temperature X-ray diffraction (HT-XRD) in moist and dry reducing atmosphere in order to prevent the competition with the oxidation reaction. Both powder and dense specimens were investigated and similar lattice parameters were obtained, demonstrating that the data were recorded on samples that were in equilibrium with the surrounding environment. Two sets of experiments were performed. In the first one, the sample was hydrated in situ in the XRD chamber at high temperature and diffraction data were collected during cooling. For the second set, the samples were pre-hydrated ex situ in an autoclave and the XRD patterns were recorded during heating under dry conditions. As expected, lattice parameters were larger for the hydrated samples, due to hydration chemical expansion. The chemical expansion was also found to be larger with the presence of Ce. Finally, larger concentrations of protonic defects were present in the lattice of the ex situ pre-hydrated samples compared with the in situ hydrated samples. [ABSTRACT FROM AUTHOR]

A novel method for the zirconoarylation of alkynes was developed. TCQ-promoted reductive elimination of arylzirconate [LiCp2ZrAr(RC≡CR)], which was prepared by the reaction of zirconocene–alkyne complexes with aryllithium compounds, afforded trisubstituted alkenylzirconocenes. This reaction can afford multi-substituted olefins with high stereoselectivity.