Dielectric probing of low-temperature degradation resistance of commercial zirconia bio-ceramics.

Objectives: To investigate the effect of the stability of oxygen vacancies on the low-temperature degradation (LTD) resistance of two kinds of commercial zirconia-based materials (3Y-TZP ceramics and Ce-TZP/AlO composites) via the dielectric probing methods.

Methods: The commercial 3Y-TZP ceramics and Ce-TZP/AlO composites were prepared via conventional solid-state methods. Density, phase content, microstructure, strain, and biaxial flexural strength (BFS) of two materials were investigated using Archimedes method, XRD, SEM, strain-electric field (S-E) loops and ball-on-ring methods, respectively.

Origin of Polarization in Bismuth Sodium Titanate-Based Ceramics.

The classical view of the structural changes that occur at the ferroelectric transition in perovskite-structured systems, such as BaTiO, is that polarization occurs due to the off-center displacement of the B-site cations. Here, we show that in the bismuth sodium titanate (BNT)-based composition 0.2(BaSrTiO)-0.

Microstructure evolution and the deformation mechanism in nanocrystalline superior-deformed tantalum.

The temperature-controlled relationship between the mechanical properties and deformation mechanism of tantalum (Ta) enables the extension of its application potential in various areas of life, including energy and electronics industries. In this work, the microstructure and deformation behavior of nanocrystalline superior-deformed Ta have been investigated in a wide temperature range. The structural analysis revealed that the high-performance Ta consists of several different substructures, with an average size of about 20 nm.

High Thermoelectric Performance Related to PVDF Ferroelectric Domains in P-Type Flexible PVDF-BiSbTe Composite Film.

There is increasing demand to power Internet of Things devices using ambient energy sources. Flexible, low-temperature, organic/inorganic thermoelectric devices are a breakthrough next-generation approach to meet this challenge. However, these systems suffer from poor performance and expensive processing preventing wide application of the technology.

Origin of the switchable photocurrent direction in BiFeO thin films.

We report external bias driven switchable photocurrent (anodic and cathodic) in 2.3 eV indirect band gap perovskite (BiFeO) photoactive thin films. Depending on the applied bias our BiFeO films exhibit photocurrents more usually found in p- or n-type semiconductor photoelectrodes.

Structure and Conductivity in LISICON Analogues within the LiGeO-LiMoO System.

New solid electrolytes are crucial for the development of all-solid-state lithium batteries with advantages in safety and energy densities over current liquid electrolyte systems. While some of the best solid-state Li-ion conductors are based on sulfides, their air sensitivity makes them less commercially attractive, and attention is refocusing on air-stable oxide-based systems. Among these, the LISICON-structured systems, such as LiZnGeO and LiVGeO, have been relatively well studied.

Local Structure in α-BIMEVOXes (ME = Ge, Sn).

The BIMEVOXes are among the best oxide ion conductors at low and intermediate temperatures. Their high conductivity is associated with local defect structure. In this work, the local structures of two BIMEVOX compositions, BiVGeO and BiVSnO, are examined using total neutron and X-ray scattering methods, with both compositions exhibiting the ordered α-phase at 25 °C and the disordered γ-phase at 700 °C.

Achieving Ultrahigh Energy Storage Density of La and Ta Codoped AgNbO Ceramics by Optimizing the Field-Induced Phase Transitions.

Energy storage capacitors are extensively used in pulsed power devices because of fast charge/discharge rates and high power density. However, the low energy storage density and efficiency of dielectric capacitors limit their further commercialization in modern energy storage applications. Lead-free AgNbO-based antiferroelectric (AFE) ceramics are considered to be one of the most promising environmentally friendly materials for dielectric capacitors because of their characteristic double polarization-electric field hysteresis loops with small remanent polarization and large maximum polarization.

Antiferroelectric-like Behavior in a Lead-Free Perovskite Layered Structure Ceramic.

Antiferroelectric (AFE) materials have been intensively studied due to their potential uses in energy storage applications and energy conversion. These materials are characterized by double polarization-electric field (-) hysteresis loops and nonpolar crystal structures. Unusually, in the present work, SrLaTaTiO (STLT32), SrLaTaTiO (STLT36), and SrCaTaO (SCT15), lead-free perovskite layered structure (PLS) materials, are shown to exhibit AFE-like double - hysteresis loops despite maintaining a polar crystal structure.

Terahertz Faraday Rotation of SrFeO Hexaferrites Enhanced by Nb Doping.

The magneto-optical and dielectric behavior of M-type hexaferrites as permanent magnets in the THz band is essential for potential applications like microwave absorbers and antennas, while are rarely reported in recent years. In this work, single-phase SrFeNbO hexaferrite ceramics were prepared by the conventional solid-state sintering method. Temperature dependence of dielectric parameters was investigated here to determine the relationship between dielectric response and magnetic phase transition.

Enhancement of Thermoelectric Performance in BiSbTe Particulate Composites Including Ferroelectric BaTiO Nanodots.

An increasing number of studies have reported producing composite structures by combining thermoelectric and functional materials. However, combining energy filtering and ferroelectric polarization to enhance the dimensionless figure of merit thermoelectric remains elusive. Here we report a composite that contains nanostructured BaTiO embedded in a BiSbTe matrix.

Grain Size Effects in Mn-Modified 0.67BiFeO-0.33BaTiO Ceramics.

Grain size can have significant effects on the properties of electroceramics for dielectric, piezoelectric, and ferroelectric applications. Here, we systematically investigate the effect of grain size on the structure and properties of Mn-modified 0.67BiFeO-0.

Terahertz Characterization of Lead-Free Dielectrics for Different Applications.

In this spotlight on applications, we describe our recent progress on the terahertz (THz) characterization of linear and nonlinear dielectrics for broadening their applications in different electrical devices. We begin with a discussion on the behavior of dielectrics over a broadband of frequencies and describe the main characteristics of ferroelectrics, as they are an important category of nonlinear dielectrics. We then move on to look at the influence of point defects, porosities, and interfaces, including grain boundaries and domain walls, on the dielectric properties at THz frequencies.

Structural Evolution in BiNbO.

The sequence of transitions between different phases of BiNbO has been thoroughly investigated and clarified using thermal analysis, high-resolution neutron diffraction, and Raman spectroscopy. The theoretical optical phonon modes of the α-phase have been calculated. Based on thermoanalytical data supported by density functional theory (DFT) calculations, the β-phase is proposed to be metastable, while the α- and γ-phases are stable below and above 1040 °C, respectively.

Terahertz Reading of Ferroelectric Domain Wall Dielectric Switching.

Ferroelectric domain walls (DWs) are important nanoscale interfaces between two domains. It is widely accepted that ferroelectric domain walls work idly at terahertz (THz) frequencies, consequently discouraging efforts to engineer the domain walls to create new applications that utilize THz radiation. However, the present work clearly demonstrates the activity of domain walls at THz frequencies in a lead-free Aurivillius phase ferroelectric ceramic, CaRbCeBiNbO, examined using THz-time-domain spectroscopy (THz-TDS).

Solution-Processed Epitaxial Growth of Arbitrary Surface Nanopatterns on Hybrid Perovskite Monocrystalline Thin Films.

Semiconductor surface patterning at the nanometer scale is crucial for high-performance optical, electronic, and photovoltaic devices. To date, surface nanostructures on organic-inorganic single-crystal perovskites have been achieved mainly through destructive methods such as electron-beam lithography and focused ion beam milling. Here, we present a solution-based epitaxial growth method for creating nanopatterns on the surface of perovskite monocrystalline thin films.

High Thermoelectric Performance in SnTe Nanocomposites with All-Scale Hierarchical Structures.

SnTe has attracted considerable attention as an environmentally friendly thermoelectric material. The thermoelectric figure of merit ZT value is related to low thermal conductivity that can be successfully realized using fabrication of nanostructures. However, the practical realization of SnTe nanostructured composites is often limited by long reaction time, low yield, and aggregation of nanoparticles.

Boosting the Thermoelectric Performance of Calcium Cobaltite Composites through Structural Defect Engineering.

Misfit-layered CaCoO as a p-type semiconductor is difficult to commercialize because of its relatively poor performance. Here, CaLaAgCoO/Ag composites prepared by spark plasma sintering were systematically investigated in terms of La dopant levels and nano-sized Ag compacts. Multiscale microstructures of stacking fault, dislocation, and oxygen vacancy-linked defects could be recognized as an effective strategy for tuning the transport of charge carriers and phonon scattering.

Ultrahigh β-phase content poly(vinylidene fluoride) with relaxor-like ferroelectricity for high energy density capacitors.

Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations.

Symmetry-mode analysis for intuitive observation of structure-property relationships in the lead-free antiferroelectric (1-)AgNbO-LiTaO.

Functional materials are of critical importance to electronic and smart devices. A deep understanding of the structure-property relationship is essential for designing new materials. In this work, instead of utilizing conventional atomic coordinates, a symmetry-mode approach is successfully used to conduct structure refinement of the neutron powder diffraction data of (1-)AgNbO-LiTaO (0 ≤ ≤ 0.

Titanium Dioxide Engineered for Near-dispersionless High Terahertz Permittivity and Ultra-low-loss.

Realising engineering ceramics to serve as substrate materials in high-performance terahertz(THz) that are low-cost, have low dielectric loss and near-dispersionless broadband, high permittivity, is exceedingly demanding. Such substrates are deployed in, for example, integrated circuits for synthesizing and converting nonplanar and 3D structures into planar forms. The Rutile form of titanium dioxide (TiO) has been widely accepted as commercially economical candidate substrate that meets demands for both low-loss and high permittivities at sub-THz bands.

Room temperature magnetoelectric coupling in intrinsic multiferroic Aurivillius phase textured ceramics.

Spark plasma sintering was employed in order to obtain textured Aurivillius phase ceramics that simultaneously exhibit ferroelectric and ferromagnetic properties at room temperature. The sintered multiferroics are layer-structured, nearly single-phase materials. Although a small amount of the secondary phase consisting of magnetic Co and Fe was detected by SEM/EDX, a majority of the observed ferromagnetic behaviour was attributed to the Aurivillius phase BiLaTiFeCoO based on the observed magnetic anisotropy.

Tuning the electrocaloric enhancement near the morphotropic phase boundary in lead-free ceramics.

The need for more energy-efficient and environmentally-friendly alternatives in the refrigeration industry to meet global emission targets has driven efforts towards materials with a potential for solid state cooling. Adiabatic depolarisation cooling, based on the electrocaloric effect (ECE), is a significant contender for efficient new solid state refrigeration techniques. Some of the highest ECE performances reported are found in compounds close to the morphotropic phase boundary (MPB).

Unfolding grain size effects in barium titanate ferroelectric ceramics.

Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO3 ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used.

Phase stability and rapid consolidation of hydroxyapatite-zirconia nano-coprecipitates made using continuous hydrothermal flow synthesis.

A rapid and continuous hydrothermal route for the synthesis of nano-sized hydroxyapatite rods co-precipitated with calcium-doped zirconia nanoparticles using a superheated water flow at 450°C and 24.1 MPa as a crystallizing medium is described. Hydroxyapatite and calcium-doped zirconia phases in the powder mixtures could be clearly identified based on particle size and morphology under transmission electron microscopy.