LiZn ferrite ceramics with high saturation magnetization (4πMs) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10–50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li0.415Zn0.27Mn0.06Ti0.1Fe2.155O4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πMs and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

A facile low-temperature crystallization method was recently developed for the synthesis of anodic TiO2 nanotubes (NTs). This novel method requires less energy and less sophisticated equipment than traditional high-temperature sintering, but the underlying mechanisms have not yet been elucidated. Here, we systematically studied the low-temperature crystallization mechanism of anodic TiO2 NTs by using different solvents and treatment time. For the first time, we notice a dramatic change of the surrounding water and discuss the TiO2 nanocrystals (NCs) byproducts of the low-temperature crystallization process. Accordingly, we propose a dissolution–recrystallization mechanism in which dissolved Ti(OH)62– dehydrates and crystallizes in situ to form anatase NTs as well as anatase NCs. Overall, this work provides a mechanistic insight into this low-temperature crystallization method, which could benefit the optimization and scale-up of industrial TiO2 NT production.

•GeSn films with medium Sn contents on silicon substrate.•In-situ high vacuum annealing were investigated.•Near infrared, mid-far infrared, and THz properties.This paper reports the use of in-situ thermal treatments to modify the properties of GeSn films and their performance in the infrared and Terahertz wave bands. The GeSn films were grown by molecular beam epitaxy under various conditions. X-ray analysis indicated the presence of amorphous phases and oxides in the GeSn films when they were epitaxially grown under low substrate temperature. Raman spectroscopy showed that the GeSn characteristic peak moved toward the larger wavenumber of 3.711 cm−1, and the intensity increased by 22.2% for the annealed GeSn (3.28% Sn) film. Moreover, it was determined from the full-wave reflection spectra that the direct band-gap is around 0.843 eV (1.47 μm). In-situ annealing accelerated the diffusion and ion substitution process of Sn atoms in the Ge lattice, which promoted the stability of the GeSn crystal cell and their optical performances in the infrared and terahertz range.

•GeSn alloy semiconductor thin films prepared by MBE method.•Near, mid and far-infrared properties were investigated.•Tera hertz of the MBE GeSn films were further discussed.Ultra-thin GeSn films with high Sn contents were epitaxial grown on single silicon substrates with different substrate temperatures by MBE method. It is found that the GeSn film with substrate temperature lower than 450 °C still represents amorphous or partially amorphous, which might lead to a volatile optical properties or I–V curve in infrared and terahertz bands. XRD measurement shows stronger GeSn single crystal peak (400) and narrower full width at half maximum (FWHM) when increase the substrate temperature during the growth. Mid and far infrared (FT-IR) test suggests that the transmission of the GeSn films get improved for about 46% when the substrate temperature increases from 200 to 450 °C. Terahertz transmission of the GeSn samples also improved with a maximum rising rate of 25%/50 °C as the substrate temperature increases. This study of GeSn substrate temperature during the growth demonstrates it is one of the key factors to control the structure stability of the GeSn films and their infrared and terahertz properties.

•Low-temperature preparation of Li–Zn–Ti ferrites (below 950 °C).•All the samples with BZBS glass addition show a typical spinel structure.•Bs increased from ∼100 to 285 mT with the ΔH decreased from 800 to 275 Oe.In this study, effects of a BaO–ZnO–B2O3–SiO2 (BZBS) glass on the ferromagnetic properties of Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites were systematically investigated. Through the solid-state reaction process, it was observed that a pure spinel phase was obtained with the sintering temperature raging from 880 °C to 920 °C, indicating the compatibility of co-firing with silver. Results revealed that the addition of BZBS glass significantly promoted grain growth and enhanced ferromagnetic properties of the Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites. With an optimized addition of BZBS glass (2.0 wt.%), the saturation induction was increased from ∼100 to 285 mT and the FMR line width at 9.3 GHz was dramatically reduced from ∼800 to 275 Oe. This study indicates that BZBS glass is a promising candidate for low temperature co-fired ceramics (LTCC).

Anodic growth of TiO2 nanotube (NT) arrays has been proved to be very promising for energy conversion applications, e.g. in photovoltaic devices and fuel cells. However, disordered “nano-grass” layers were always found on the top of the anodic TiO2 NT arrays. In this paper, we demonstrate a novel and simple method using a micromechanical cleavage technique to peel off the disordered nanograss layer. Using this method, ∼1 × 1.5 cm−2 of uncapped TiO2 NT arrays with a high-aspect ratio can be easily obtained. The results further indicate that the treatment can improve the photovoltaic and photochemical performances. After the treatment, the conversion efficiency (η) of the dye sensitized solar cells (DSSCs) increased by 29.3%. This work facilitates the growth and applications of high aspect-ratio anodic TiO2 NT arrays in related devices and systems.

The fabrication and photocatalytic properties of visible-light driven CuInSe2/TiO2 heterojunction films are reported. CuInSe2 nanoparticles (NCs) were synthesized using a solvothermal method and then decorated onto self-organized anodic TiO2 nanotube (NT) arrays through an electrophoretic deposition process, forming a CuInSe2 NC/TiO2 NT hetero-structure film. An increase in deposition time produced an increased amount of CuInSe2 NCs loaded onto the TiO2 NT arrays, expanding the light-absorption range of the CuInSe2 NCs/TiO2 NTs film from 400 nm to 700 nm. Photocatalytic degradation results show that activities of the CuInSe2 NCs/TiO2 NTs films were significantly enhanced compared to that of pure TiO2 NTs (degradation rate constant k increased from 3 × 10-3 min-1 to >1 × 10-2 min-1). Particularly, the CuInSe2 NCs/TiO2 NTs with 50 min electrophoretic deposition show the highest degradation rate, k = 1.6 × 10-2 min-1 (more than 5 times greater than that of the pure TiO2 NTs film), due to optimization of CuInSe2 NCs loading and a well-maintained open TiO2 tube-mouth configuration.Keywords: CuInSe2 nanocrystals; heterojunctions; photocatalytic activity; TiO2 nanotubes;

Anodic growth of TiO2 nanotube (NT) arrays has been proved to be very promising for energy conversion applications, e.g. in photovoltaic devices and fuel cells. However, disordered “nano-grass” layers were always found on the top of the anodic TiO2 NT arrays. In this paper, we demonstrate a novel and simple method using a micromechanical cleavage technique to peel off the disordered nanograss layer. Using this method, ∼1 × 1.5 cm−2 of uncapped TiO2 NT arrays with a high-aspect ratio can be easily obtained. The results further indicate that the treatment can improve the photovoltaic and photochemical performances. After the treatment, the conversion efficiency (η) of the dye sensitized solar cells (DSSCs) increased by 29.3%. This work facilitates the growth and applications of high aspect-ratio anodic TiO2 NT arrays in related devices and systems.