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Magnetocaloric materials can be useful in magnetic refrigeration applications, but to be practical the magneto-refrigerant needs to have a very large magnetocaloric effect (MCE) near room temperature for modest applied fields (<2 T) with small hysteresis and magnetostriction, and should have a complete magnetic transition, and environmentally friendly. One system that may fulfill these requirements is Mn 2- x Fe x P 1- y Ge y , where a combined first-order structural and magnetic transition occurs between the high temperature paramagnetic and low temperature ferromagnetic phase. We have used neutron diffraction, differential scanning calorimetry, and magnetization measurements to study the effects of Mn and Ge location in the structure on the ordered magnetic moment, MCE, and hysteresis for a series of compositions of the system near optimal doping. The diffraction results indicate that the Mn ions located on the 3 f site enhance the desirable properties, while those located on the 3 g sites are detrimental. The phase fraction that transforms, hysteresis of the transition, and entropy change can be affected greatly by both the compositional homogeneity and the particle size, and an annealing procedure has been developed that substantially improves the performance of all three properties of the material. We also establish a correlation between applied magnetic field to complete the transition and the temperature range of coexistence of the PM and FM phase. On the basis of these results we have identified a pathway to understand the nature and to optimize the MCE properties of this system for magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

Abstract: A composite of SrTiO3/TiO2 was successfully prepared using TiO2 (Degussa P25) and SrTiO3 powders as starting materials. The composite was characterized by X-ray diffraction (XRD), UV–vis absorption spectrum, scanning electron microscope (SEM), and surface photovoltage spectroscopy (SPS). The SrTiO3/TiO2 composite presents an enhanced photovoltaic response compared with pure TiO2 and SrTiO3. The enhancement was explained by investigating the energy levels of TiO2 and SrTiO3, and the photoluminescence (PL) spectra of TiO2, SrTiO3 and SrTiO3/TiO2. The analysis of energy levels shows that those of TiO2 and SrTiO3 are matching, which improves the separation efficiency of photogenerated carriers. The PL spectra indicate that the formation of SrTiO3/TiO2 composite decreases the recombination rate of photogenerated carriers. Thus the photovoltaic response enhancement is mainly resulting from the improved separation efficiency and decreased recombination rate of photogenerated carriers for SrTiO3/TiO2 composite. [Copyright &y& Elsevier]

Highlights: [•] Ce3+/Yb3+ co-doped oxyfluoride glasses are synthesized by melt-quenching method. [•] NIR emission under 322nm excitation indicates energy transfer from Ce3+ to Yb3+. [•] Efficient quantum cutting with the maximum quantum efficiency of 191% is obtained. [Copyright &y& Elsevier]

Spall damage of Ti-6Al-4V alloy fabricated via laser powder bed fusion (LPBF) is investigated via plate impact along the build direction (BD) and the transverse direction (TD), as regards its underlying mechanisms and microstructure effects. Conventional hot-rolled Ti-6Al-4V alloys processed with annealing and quenching are also examined for comparison. Hugoniot elastic limit (HEL) and spall strength of the LPBF-fabricated samples are derived from free-surface velocity histories, and are higher for the TD loading than for the BD loading. The LPBF-fabricated alloy has a lower HEL but similar spall strength compared to the conventionally fabricated alloys. Quantitative analysis of recovered samples reveals that, the number of cracks is smaller and the mean crack length is larger in the LPBF-fabricated and quenched hot-rolled samples containing α ′ martensite laths than the annealed hot-rolled sample containing equiaxed α grains. For the LPBF-fabricated samples, the TD loading induces cracks of similar length along α ′ grain boundaries (GBs) and α ′ { 0001 } planes, but much longer cracks along prior β GBs compared to the BD loading. Anisotropy in mechanical properties and damage is due to columnar prior β grains, morphological and crystallographic texture of α ′ laths. • AM-fabricated and conventional Ti-6Al-4 V have comparable mechanical property. • Coherent lath boundaries have higher resistance to crack nucleation than random GBs. • Cracks tend to propagate along lath boundaries or random GBs or α ′ { 0001 } planes. • Cracks can propagate across lath boundaries but not random GBs. [ABSTRACT FROM AUTHOR]

We studied the influence of Al doping on the crystal structure and magnetocaloric properties of Mn 1.2 Fe 0.8 P 1 − x Ge x Al y compounds prepared by spark plasma sintering, with x = 0.24, 0.25, 0.26 and y = 0, 0.004, 0.008, 0.010 or 0.12. These compounds have the same Fe 2 P-type structure (space group P 6 ¯ 2m ) as the undoped system, and we found that the addition of Al had significant effects on the hexagonal unit cell of the compound and its physical properties. As y increased, the lattice parameter a and cell volume increased, the lattice parameter c decreased, the thermal hysteresis (Δ T hys ) decreased, and the Curie temperature ( T c ) became significantly higher than at y = 0. The variations of T c and Δ T hys correlated almost linearly with variation in the c / a ratio, indicating that T c can be increased with Al doping. In addition, Al doping did not have any adverse effects on other magnetocaloric properties, such as the entropy change, adiabatic temperature change, and the temperature range of the coexistence of the paramagnetic and ferromagnetic phases. We also found that the magnetocaloric properties of Mn 1.2 Fe 0.8 P 1 − x Ge x Al y compounds could be improved by homogenous annealing. The particular composition Mn 1.2 Fe 0.8 P 0.74 Ge 0.26 Al 0.010 exhibited a T c close to room temperature (292.2 K) with a hysteresis of Δ T hys 2.1 K, making it a very promising material for magnetic refrigeration around room temperature. [ABSTRACT FROM AUTHOR]

Novel low temperature sintered Li 4 Mg 3 [Ti 0.8 (Mg 1/3 Ta 2/3) 0.2 2 O 9 (LMT 0.8 (MT) 0.2) ceramics with 1–5 wt% LiF additives were successfully prepared by the solid-state reaction method. The effects of LiF additives on the phase composition, sintering characteristic, microstructure and microwave dielectric properties of LMT 0.8 (MT) 0.2 ceramics were investigated in detail for the first time. The sintering temperature of LMT 0.8 (MT) 0.2 ceramics could be effectively lowered to 950 °C by the addition of LiF. A single rock salt crystalline phase structure belonging to a space group of Fm-3m (No.225) was obtained through X-ray diffraction patterns. Dense uniform morphology was observed at 950 °C for LMT 0.8 (MT) 0.2 ceramics with 3–5 wt% LiF in terms of scanning electron microscopy photographs. Particularly, the LMT 0.8 (MT) 0.2 -4 wt% LiF ceramics sintered at 950 °C for 4 h possessed optimum microwave dielectric properties of ε r = 16.10, Q·f = 114,313 GHz (at 8.18 GHz) and τ f = −7.72 ppm/°C. In addition, the excellent chemical compatibility with silver metal electrodes indicated that the LMT 0.8 (MT) 0.2 -4 wt% LiF ceramics might be a promising candidate for the low-loss low temperature co-fired ceramics (LTCC) applications in microwave devices. Image 1 • The low-fired LiF-doped Li 4 Mg 3 [Ti 0.8 (Mg 1/3 Ta 2/3) 0.2 2 O 9 composite ceramics are fabricated. • LiF-doping lowered sintering temperature of Li 4 Mg 3 [Ti 0.8 (Mg 1/3 Ta 2/3) 0.2 2 O 9 ceramics to 950 °C. • Li 4 Mg 3 [Ti 0.8 (Mg 1/3 Ta 2/3) 0.2 2 O 9 -4 wt% LiF ceramics exhibited good dielectric properties. • The sample was compatible with Ag electrodes and suitable for LTCC applications. [ABSTRACT FROM AUTHOR]