Explore the vast range of titles available.

The (Ba0.85Ca0.15) (Ti0.90Zr0.10)O3 + x Y3+ + x Nb5+ (abbreviated as BCZT-x(Nb + Y), x = 0 mol%, 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.3 mol%) lead-free piezoceramics samples were prepared by a traditional solid-state sintering method. And the effects of Yttrium and Niobium elements (Y3+ and Nb5+) co-doping on the defect, phase and structure, microstructure, and comprehensive electrical properties have been investigated. Research results show that the Y and Nb elements co-doping can dramatically enhance piezoelectric properties. It is worth noting that XPS defect chemistry analysis, XRD phase analysis and TEM results together show that a new phase of double perovskite structure Barium Yttrium Niobium Oxide (Ba2YNbO6) is formed in the ceramic, and the XRD Rietveld refinement and TEM results show the coexistence of the R-O-T phase. Both these two reasons together lead to significant performance improvements of piezoelectric constant (d33) and planar electro-mechanical coupling coefficient (kp). The functional relation between temperature and dielectric constant testing results present that the Curie temperature increases slightly, which shows the same law as the change of piezoelectric properties. The ceramic sample reaches an optimal performance at x = 0.1% of BCZT-x(Nb + Y), where d33 = 667 pC/N, kp = 0.58, εr = 5656, tanδ = 0.022, Pr = 12.8 μC/cm2, EC = 2.17 kV/cm, TC =92 °C, respectively. Therefore, they can be used as potential alternative materials to lead based piezoelectric ceramics.

Methods for the synthesis of iron oxide nanoparticles with various modifications (magnetite, maghemite, hematite) and iron-containing nanoparticles with perovskite structure are considered. Particular attention is paid to the method based on the use of microwave radiation, as the most efficient, low-energy method, resulting in the preparation of nanoparticles with a narrow size distribution and a small particle size.

AbstractDue to the complexity of obtaining micro- and nanoscale objects, data on the structure and properties of such materials are especially important. This makes it relevant to use computer modeling to predict the required characteristics of materials. The electronic, magnetic, mechanical, and other properties of crystalline substances are determined by the specificity of their structure: the periodicity and symmetry of the lattice. This paper considers compounds with the common chemical formulas ABO3 and A2BB'O6, as well as the crystal lattice of the cubic symmetry type: the structural types Perovskite and Double Perovskite. The model of ionatomic radii, widely used in modeling various crystal structures, is applied. The application of the annealing simulation algorithm to calculate the metric parameters of the compounds under consideration is shown. The software implementation of the algorithm used in the study makes it possible to calculate the coordinates of the atoms included in the elementary cell of the crystal lattice, the lattice constant, and the packing density of atoms in the crystal cell according to the given chemical formula and the spatial symmetry group. The listed structural characteristics can be used for the subsequent determination of the electronic, magnetic, and thermal properties of perovskite-like compounds. This article presents a comparison of the values of the lattice constants obtained as a result of numerical modeling with the data published in open sources.

Two sets of Nd-doped La 0.7 Sr 0.3 MnO 3 nanoparticles were synthesized via sol-gel method with further heat treatment at 1073 and 1573 K, respectively. Crystallographic and magnetic properties of obtained nanoparticles were studied, and the effect of synthesis conditions on these properties was investigated. According to X-ray data, all particles crystallized in the distorted perovskite structure. Magnetic parameters, such as saturation magnetization, coercivity, Curie temperature, and specific loss power, which is released on the exposure of an ensemble of nanoparticles to AC magnetic field, were determined for both sets of samples. The correlation between the values of Curie temperature and maximal heating temperature under AC magnetic field was found. It was revealed that for the samples synthesized at 1573 K, the dependences of crystallographic and magnetic parameters on Nd content were monotonous, while for the samples synthesized at 1073 K, they were non-monotonous. It was concluded that Nd-doped La 0.7 Sr 0.3 MnO 3 nanoparticles are promising materials for self-controlled magnetic hyperthermia applications, but the researchers should be aware of the unusual behavior of the particles synthesized at relatively low temperatures.

The effect of isomorphic substitution of atoms on crystal structure and properties of oxide compounds is one of the main tasks of modern materials science. This work is devoted to the study of Ba atoms by smaller Sr atoms’ substitution in two-slab perovskite-like structure of BaNd2In2O7 and its effect on the structural features and electroconductive properties of the Ba1−xSrxNd2In2O7 indates synthesized. A characterization, including data of X-ray diffraction, structural calculations (Rietveld method) of phases obtained, is presented. Existence region of Ba1−xSrxNd2In2O7 solid solutions with a two-slab perovskite-like structure (0 ≤ x ≤ 0.2) was established and their coordinate parameters (x = 0.1 and x = 0.2) are refined. Ba1−xSrxNd2In2O7 structure is based on two-dimensional (infinite in the XY plane) perovskite-like blocks of two slabs connected by vertices of deformed InO6 octahedra. Neighbouring blocks are separated by a slab of NdO9 polyhedra and interconnected by O–Nd–O bonds. Correlations between substitution degree of barium atoms and electroconductive properties have been established. It is shown that such type of substitution leads to a decrease in the Nd–O2 interblock bond length (from 0.223(2) nm at x = 0 to 0.214(1) nm at x = 0.2). This brings the constitution of two-dimensional structure of Ba1−xSrxNd2In2O7 closer to the structure of three-dimensional perovskite and leads to its destruction at x > 0.2. Increase in the degree of substitution is also accompanied by a gradual decrease in specific conductivity of ceramic grains and increase in the activation energy and their own electrical conductivity.

Perovskite solar cells (PSC) have been identified as a game-changer in the world of photovoltaics. This is owing to their rapid development in performance efficiency, increasing from 3.5% to 25.8% in a decade. Further advantages of PSCs include low fabrication costs and high tunability compared to conventional silicon-based solar cells. This paper reviews existing literature to discuss the structural and fundamental features of PSCs that have resulted in significant performance gains. Key electronic and optical properties include high electron mobility (800 cm2/Vs), long diffusion wavelength (>1 μm), and high absorption coefficient (105 cm−1). Synthesis methods of PSCs are considered, with solution-based manufacturing being the most cost-effective and common industrial method. Furthermore, this review identifies the issues impeding PSCs from large-scale commercialisation and the actions needed to resolve them. The main issue is stability as PSCs are particularly vulnerable to moisture, caused by the inherently weak bonds in the perovskite structure. Scalability of manufacturing is also a big issue as the spin-coating technique used for most laboratory-scale tests is not appropriate for large-scale production. This highlights the need for a transition to manufacturing techniques that are compatible with roll-to-roll processing to achieve high throughput. Finally, this review discusses future innovations, with the development of more environmentally friendly lead-free PSCs and high-efficiency multi-junction cells. Overall, this review provides a critical evaluation of the advances, opportunities and challenges of PSCs.

The perovskite structure accommodates many different combinations of elements, making it attractive for use in a wide variety of applications. Building perovskites out of only organic compounds is appealing because these materials tend to be flexible, fracture-resistant, and potentially easier to synthesize than their inorganic counterparts. Ye et al. describe a previously unknown family of all-organic perovskites, of which they synthesized 23 different family members (see the Perspective by Li and Ji). The compounds are attractive as ferroelectrics, including one compound with properties close to the well-known inorganic ferroelectric BaTiO 3 . Science , this issue p. 151 ; see also p. 132 A family of all-organic perovskites has attractive ferroelectric properties. Inorganic perovskite ferroelectrics are widely used in nonvolatile memory elements, capacitors, and sensors because of their excellent ferroelectric and other properties. Organic ferroelectrics are desirable for their mechanical flexibility, low weight, environmentally friendly processing, and low processing temperatures. Although almost a century has passed since the first ferroelectric, Rochelle salt, was discovered, examples of highly desirable organic perovskite ferroelectrics are lacking. We found a family of metal-free organic perovskite ferroelectrics with the characteristic three-dimensional structure, among which MDABCO ( N -methyl- N' -diazabicyclo[2.2.2]octonium)–ammonium triiodide has a spontaneous polarization of 22 microcoulombs per square centimeter [close to that of barium titanate (BTO)], a high phase transition temperature of 448 kelvins (above that of BTO), and eight possible polarization directions. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.

The mechanism of superconductivity in cuprates remains one of the big challenges of condensed matter physics. High-Tc cuprates crystallize into a layered perovskite structure featuring copper oxygen octahedral coordination. Due to the Jahn Teller effect in combination with the strong static Coulomb interaction, the octahedra in high-Tc cuprates are elongated along the c axis, leading to a 3dx²-y² orbital at the top of the band structure wherein the doped holes reside. This scenario gives rise to 2D characteristics in high-Tc cuprates that favor d-wave pairing symmetry. Here, we report superconductivity in a cuprate Ba₂CuO4-y, wherein the local octahedron is in a very exceptional compressed version. The Ba₂CuO4-y compound was synthesized at high pressure at high temperatures and shows bulk superconductivity with critical temperature (Tc ) above 70 K at ambient conditions. This superconducting transition temperature is more than 30 K higher than the Tc for the isostructural counterparts based on classical La₂CuO₄. X-ray absorption measurements indicate the heavily doped nature of the Ba₂CuO4-y superconductor. In compressed octahedron, the 3d3z²-r² orbital will be lifted above the 3dx²-y² orbital, leading to significant 3D nature in addition to the conventional 3dx²-y² orbital. This work sheds important light on advancing our comprehensive understanding of the superconducting mechanism of high Tc in cuprate materials.

Quasi-two-dimensional (quasi-2D) Ruddlesden–Popper (RP) perovskites such as BA 2 Cs n –1 Pb n Br 3 n +1 (BA = butylammonium, n  > 1) are promising emitters, but their electroluminescence performance is limited by a severe non-radiative recombination during the energy transfer process. Here, we make use of methanesulfonate (MeS) that can interact with the spacer BA cations via strong hydrogen bonding interaction to reconstruct the quasi-2D perovskite structure, which increases the energy acceptor-to-donor ratio and enhances the energy transfer in perovskite films, thus improving the light emission efficiency. MeS additives also lower the defect density in RP perovskites, which is due to the elimination of uncoordinated Pb 2+ by the electron-rich Lewis base MeS and the weakened adsorbate blocking effect. As a result, green light-emitting diodes fabricated using these quasi-2D RP perovskite films reach current efficiency of 63 cd A −1 and 20.5% external quantum efficiency, which are the best reported performance for devices based on quasi-2D perovskites so far. Owing to large exciton binding energy, quasi-2D perovskite is promising for light-emitting application, yet inhomogeneous phases distribution limits the potential. Here, the authors improve the performance by using MeS additive to regulate the phase distribution and to reduce defect density in the films.

Although high-entropy materials are excellent candidates for a range of functional materials, their formation traditionally requires high-temperature synthetic procedures of over 1,000 °C and complex processing techniques such as hot rolling 1 – 5 . One route to address the extreme synthetic requirements for high-entropy materials should involve the design of crystal structures with ionic bonding networks and low cohesive energies. Here we develop room-temperature-solution (20 °C) and low-temperature-solution (80 °C) synthesis procedures for a new class of metal halide perovskite high-entropy semiconductor (HES) single crystals. Due to the soft, ionic lattice nature of metal halide perovskites, these HES single crystals are designed on the cubic Cs 2 MCl 6 (M=Zr 4+ , Sn 4+ , Te 4+ , Hf 4+ , Re 4+ , Os 4+ , Ir 4+ or Pt 4+ ) vacancy-ordered double-perovskite structure from the self-assembly of stabilized complexes in multi-element inks, namely free Cs + cations and five or six different isolated [MCl 6 ] 2– anionic octahedral molecules well-mixed in strong hydrochloric acid. The resulting single-phase single crystals span two HES families of five and six elements occupying the M-site as a random alloy in near-equimolar ratios, with the overall Cs 2 MCl 6 crystal structure and stoichiometry maintained. The incorporation of various [MCl 6 ] 2– octahedral molecular orbitals disordered across high-entropy five- and six-element Cs 2 MCl 6 single crystals produces complex vibrational and electronic structures with energy transfer interactions between the confined exciton states of the five or six different isolated octahedral molecules. Room-temperature-solution (20 °C) and low-temperature-solution (80 °C) synthesis procedures are developed for a new class of metal halide perovskite high-entropy semiconductor single crystals.