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Dopant-free, transparent ZrO 2 with a monoclinic structure was successfully developed through a two-step oxidation process by combining heat treatment in air and under a low oxygen partial pressure, using a Zr metal foil. The transmission of the sample was ~50% at 600 nm (in the region of visible light) and over 60% beyond the near-infrared region. This transparent ZrO 2 with a monoclinic structure comprised equiaxed grains with dimensions of tens of nanometers and columnar grains with lengths of several micrometers. Moreover, it formed a dense film without cracks or voids, having fewer oxygen deficiencies. Figure (a) Appearance and (b) cross-sectional SEM images of black-ZrO 2 annealed at 800 °C for 15 min in air. (c) Appearance and (d) cross-sectional SEM images of transparent-ZrO 2 annealed at 800 °C for 15 min in air, followed by heat-treatment (900 °C for 15 h in PO 2 = 1 × 10−6 atm) Image, graphical abstract [ABSTRACT FROM AUTHOR]

Silver nanowire networks on polymeric substrates have applications for flexible displays. However their electrical sheet resistance, R s , increases with increasing flexural strain cycles. A percolation model gives R s = R n (c ¯) − 2 , where c ¯ is the mean network coverage and R n is the network resistance, determined by the dimensions and electrical resistance of the individual nanowires. Network resistance is independent of coverage and increases with strain cycles, showing two clear regimes following the onset of damage after about 100 cycles. The results indicate that fatigue damage is dominated by a loss in network connectivity rather than a change in the electrical properties of individual nanowires. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Oxygen-containing yttrium hydride films (YHx:O) show interesting photochromic properties under ultraviolet irradiation. In this paper, oxygen-containing yttrium hydride films covered with tungsten oxide were prepared by a direct current magnetron sputtering method. This composite material showed reversible photochromic properties. Furthermore, its coloration speed was faster than that of a single layer of yttrium hydride, and its switching modulation was broader. The photochromic mechanism of the YHx:O/WO 3 thin films was investigated by X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy analysis. Oxygen and hydrogen played a key role in the photochromic process of the YH x :O/WO 3 composite films. [ABSTRACT FROM AUTHOR]

A wet-chemical synthesis and microwave calcination approach was found to be efficient for synthesizing α-alumina powders and polycrystals with high levels of lattice defects. The defects of the as-produced powders were determined from the optical transmittance of spark-plasma-sintered compacts with an identical microstructure using a conventional calcination method. The existence of a high lattice defect concentration was verified by positron annihilation lifetime analysis and X-ray diffraction. The microwave-activated lattice defect phenomenon has potential applications in the production of semiconductor materials or films with high chemical activity or crystal doping. [ABSTRACT FROM AUTHOR]

A translucent α/β Si3N4 composite, consisting of 85% α-Si3N4 and 15% β-Si3N4, was fabricated by hot-pressing at 1563°C for 1h, using an MgSiN2 additive. The α/β Si3N4 composite achieves a maximum transmittance of 66% for a 0.42mm thick specimen in the medium infrared region, which is attributed to its high density and to a small amount of intergranular phase and β-Si3N4. In addition to optical transmittance, the sample showed a very high hardness of 24.0±0.5GPa. [ABSTRACT FROM AUTHOR]

One-dimensional gold nanoparticle assemblies (GNAs) were deposited in unidirectionally aligned mesochannels of an SiO2 film. The unidirectivity of GNAs was confirmed by the surface and cross-sectional electron microscope images of the film. Two kinds of one-dimensional GNAs were prepared, and their anisotropic surface plasmon resonance was measured with polarized transmission spectroscopy. The polarization effects of the GNA-deposited SiO2 films were observed at individual wavelengths, which were strongly dependent on the morphology of the GNAs in the film. [ABSTRACT FROM AUTHOR]

A novel method for preparing highly transparent hydroxyapatite bioceramics at relatively low temperatures (325–450°C), i.e. about 60% lower compared with other commonly used preparation methods, has been developed under ultrahigh pressure (UHP; 2.0–5.0GPa). UHP can remarkably restrain grain growth, enhance density and microhardness and we have characterized the morphology, density and mechanical properties of the prepared ceramics. We reason that these bioceramics are highly transparent due to the negligible light scattering from the nanosized grains and pores in the samples. [Copyright &y& Elsevier]

Optical transparency in polycrystalline ceramic oxides can be achieved if the material is fully densified. Spark plasma sintering (SPS) of oxide nanoparticles leads to immediate densification with final-stage sintering. Further densification by annihilation of the isolated pores is associated with diffusional processes, regardless of the densification mechanism during the intermediate stage. Densification equations in conjunction with the concept of grain boundary free volume were used to derive the pore size–grain size–temperature map for designing the nanopowder and SPS process parameters to obtain transparent oxides. [Copyright &y& Elsevier]

Doping alumina particles with aluminum alkoxides allows dense spark plasma sintered (SPSed) materials to be obtained that have a refined grain size compared to pure materials, which is critical for their transparency. An optical model considering pore and grain size distributions has been developed to obtain information about porosity in dense materials. This work suggests that the atomic diffusion mechanisms do not depend on the sintering technique. A reduction in the activation energy by a factor of 2 has been found in SPSed materials. [Copyright &y& Elsevier]

A two-step pressure profile was used to prepare transparent MgAl2O4 ceramic without sintering aids by spark plasma sintering (SPS) at 1300°C for 3min. The influence of the pressure profile was investigated systematically and the discoloration in the present study was attributed to the dislocation formed during the fast densification in SPS. At low pre-load pressure, 5MPa, with the normal characteristic fast heating rate (100°Cmin−1), high inline transmittance of 51% at 550nm and 85% at 2000nm can be achieved. [Copyright &y& Elsevier]

Transparent spinel can be fabricated without any sintering aids by spark plasma sintering (SPS) processing for only a 20min soak at 1300°C. For heating rates <10°Cmin−1, the spinel exhibits an in-line transmission of 47% for a visible-wavelength of 550nm and a fracture strength of ∼500MPa. By means of low heating rate SPS processing, high transmission and strength can be attained mainly by reducing the residual pores to <0.5%. [Copyright &y& Elsevier]

The influence of coarse powder on grain growth during hot isostatic pressing (HIP) was examined. Powder mixtures containing 0%, 0.5%, 5% and 20% coarse powder were prepared. The magnesia sintered without pressure was subjected to HIP at 1600°C for 0.5h at different pressures. The samples produced from fine powder had the largest grains after HIP treatment, although they had the smallest grains before it. The optical transparency of the HIP-treated magnesia ceramics increased with grain size. [Copyright &y& Elsevier]

A fully dense Y2O3–MgO nanocomposite with a grain size below 100nm was successfully sintered using a sol–gel-processed nanopowder with a grain size below 30nm. The nanocomposite has an excellent transmission (∼80%) in the infrared range. The nanocomposite is highly sensitive to the annealing environment in air or vacuum. The optical transmission is reversible by changing the annealing atmosphere from vacuum to air. Based on this combined with X-ray diffraction analysis, it is reasoned that oxygen vacancy is responsible for the optical properties of the composite. [Copyright &y& Elsevier]