Innovative materials for phosphor converted white light-emitting diodes are in high demand owing to the huge potential of the light-emitting diode technology to reduce energy consumption worldwide. As the primary blue diode is already highly optimized, the conversion phosphors are of crucial importance for any further improvements. We report on the discovery of the high performance red phosphor Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ meeting all requirements for a phosphor’s optical properties. It combines the optimal spectral position for a red phosphor, as defined in the 2016 Research & Development-plan of the United States government, with an exceptionally small spectral full width at half maximum and excellent thermal stability. A white mid-power phosphor-converted light-emitting diode prototype utilising Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ shows an increase of 16% in luminous efficacy compared to currently available commercial high colour-rendering phosphor-converted light-emitting diodes, while retaining excellent high colour rendition. This phosphor enables a big leap in energy efficiency of white emitting phosphor-converted light-emitting-diodes.

This study compared shear bond strengths of six self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion. One hundred twenty zirconia samples were air-abraded (group SB; n = 60) or left untreated (group NO). Composite cylinders were bonded to the zirconia samples with either BisCem (BC), Maxcem (MC), G-Cem (GC), RelyX Unicem Clicker (RUC), RelyX Unicem Applicator (RUA), or Clearfil SA Cement (CSA). Shear bond strength was tested after thermocycling, and data were analyzed with analysis of variance and Holm-Sidak pairwise comparisons. Without abrasion, RUA (8.0 MPa), GC (7.9 MPa), and CSA (7.6 MPa) revealed significantly higher bond strengths than the other cements. Air-particle abrasion increased bond strengths for all test cements (p < 0.001). GC (22.4 MPa) and CSA (18.4 MPa) revealed the highest bond strengths in group SB. Bond strengths of self-adhesive resin cements to zirconia were increased by air-particle abrasion. Cements containing adhesive monomers (MDP/4-META) were superior to other compositions.

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While the influence of silicate oxide glass composition on its chemical durability is increasingly known, the contribution of structure only is less well understood, yet is crucial for an accurate description of aqueous alteration mechanisms. The effect of structural disorder can be investigated by varying the thermal history of the glass. Furthermore, the structural changes generated by selfirradiation in nuclear glasses can be compared with those induced by fast quenching. In the context of deep geological disposal of vitreous matrices, it is then challenging to address the structural impact on glass durability. Here, a borosilicate glass, the International Simple Glass, was fiberized to obtain a rapidly quenched sample. The quenching rate and fictive temperature were evaluated from in situ Raman and Brillouin spectroscopies. Multinuclear nuclear magnetic resonance was used to obtain insight into the effect of quenching on the pristine and altered glass structure. Higher bond angle distribution and lower mixing of alkalis were observed in the fast quenched glass. Some of AlO 4 groups are then Ca-compensated, while a part of BO 4 is transformed into BO 3 units. The structural modifications increase the hydrolysis of the silicate network occurring in the forward rate regime at 90°C by a factor of 1.4-1.8 depending on the pH value. Residual rate regime is similarly affected, more significantly at the beginning of the experiments conducted in silica saturated solutions. These findings prove that the reactivity of glass remains controlled by its structure under the various alteration regimes.

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This paper focuses on the preparation of a new extended set of calibrations of cooling rate (fictive temperature) in fused silica determined by inelastic light scattering and its subsequent use to characterize the local cooling rate distribution in ultra-short pulsed (USP) laser modification. In order to determine the thermal history (e.g. cooling rate and fictive temperature) of fused silica, high-resolution inelastic light-scattering experiments (Raman and Brillouin spectroscopy) were investigated. Calibrations were performed and compared to the existing literature to quantify structural changes due to a change of fictive temperature. Compared to existing calibrations, this paper provides an extension to lower and higher cooling rates. Using this new set of calibrations, we characterized a USP laser modification in fused silica and calculated the local fictive temperature distribution. An equation relating the fictive temperature (Tf ) to cooling rates is given. A maximum cooling rate of 3000 K min−1 in the glass transition region around 1200 °C was deduced from the Raman analysis. The Brillouin observations are sensitive to both the thermal history and the residual stress. By comparing the Raman and Brillouin observations, we extracted the local residual stress distribution with high spatial resolution. For the first time, combined Raman and Brillouin inelastic light scattering experiments show the local distribution of cooling rates and residual stresses (detailed behavior of the glass structure) in the interior and the surrounding of an USP laser modified zone.

External thermal, electrical, and mechanical fields can induce structural phase transitions in lead-free Li-modified Na 0.5 K 0.5 NbO 3 ferroelectrics, which significantly influence the macroscopic electromechanical response. In particular, the relative stability of the polar monoclinic (or orthorhombic) and tetragonal phases under temperature and stress is critical to realize the ferroelectric and piezoelectric response. In this study, the effect of mechanical and thermal fields on the local structure in the vicinity of the monoclinic-tetragonal (M-T) phase boundary was investigated using a novel in situ combined uniaxial compressive stress-and temperature-dependent Raman spectroscopy experimental arrangement. Experiments were performed up to 300 • C and −200 MPa, clearly demonstrating stress-induced M-T phase transition in Li-modified Na 0.5 K 0.5 NbO 3 . A stress-temperature phase diagram has been established based on the change in vibrational modes. It was possible to correlate the relative permittivity singularities previously observed to a given stage of the M-T phase transition using ratio between characteristic Raman band areas. In addition, the measurement method reported here can be applied to other functional ceramics to investigate the influence of mechanical fields on local structure.

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