Influence of Isostatic Pressure on the Elastic and Electronic Properties of K2SiF6:Mn4+

Isostatic pressure effects on the elastic and electronic properties of non-doped and Mn4+-doped K2SiF6 (KSF) have been investigated by first-principles calculations within density functional theory (DFT). Bulk modulus was obtained by the Murnaghan’s equation of states (EOS) using the relationship between volume and pressures at pressures between 0 and 40 GPa, and elastic constants were calculated by the stress–strain relationship giving small distortions at each pressure point. The other elastic parameters such as shear modulus, sound velocity and Debye temperature, which can be obtained from the elastic constants, were also estimated. The influence of external isostatic pressure on the electronic properties, such as crystal field strength 10Dq and emission energy of 2E → 4A2 transition (Eem), of KSF:Mn4+ was also studied. The results suggest that 10Dq and Eem linearly increase and decrease, respectively, with increasing pressure.

Application of multi-edge HERFD-XAS to assess the uranium valence electronic structure in potassium uranate (KUO3)

The uranium valence electronic structure in the prototypical undistorted perovskite KUO3 is reported on the basis of a comprehensive experimental study using multi-edge HERFD-XAS and relativistic quantum chemistry calculations based on density functional theory. Very good agreement is obtained between theory and experiments, including the confirmation of previously reported Laporte forbidden f–f transitions and X-ray photoelectron spectroscopic measurements. Many spectral features are clearly identified in the probed U-f, U-p and U-d states and the contribution of the O-p states in those features could be assessed. The octahedral crystal field strength, 10Dq, was found to be 6.6 (1.5) eV and 6.9 (4) eV from experiment and calculations, respectively. Calculated electron binding energies down to U-4f states are also reported.

Spectral and thermometric properties altering through crystal field strength modification and host material composition in luminescence thermometers based on Fe3+ doped AB2O4 type nanocrystals (A = Mg, Ca; B = Al, Ga)

The influence of the crystal field strength and host material composition on the spectral position of the emission band and thermal stability of Fe3+ luminescence was investigated in order to develop a highly sensitive luminescence thermometer.

Deep-red emitting Mg2TiO4:Mn4+ phosphor ceramics for plant lighting

In this study, deep-red emitting Mg2TiO4:Mn4+ phosphor ceramics were synthesized by the high temperature solid-state reaction method. The ceramics can be excited by the 465 nm blue light and had a narrow emission with a full width at half maximum (FWMH) value of 31 nm. The peak wavelength was located at 658 nm, which matched the demanded wavelength for photosynthesis. The crystal field strength (Dq) and the Racah parameters (B and C) were estimated by the Tanabe-Sugano diagram. The thermal conductivity of the Mg2Ti(0.999)O4:0.001Mn4+ ceramic was 7.535 W/(m·K) at room temperature, which was one order of magnitude higher than that of the traditional packaging method using the silicone gel. A set of phosphor converted LEDs were fabricated by mounting the phosphor ceramics onto the 460 nm blue LED chips and the CIE coordinates can move from the blue region to the purple light region with the thickness of the ceramic increasing. These results indicated that the Mg2TiO4:Mn4+ phosphor ceramic was suitable for plant lighting when combined with a blue LED chip.

Deep-red emitting Mg2TiO4:Mn4+ phosphor ceramics for plant lighting

In this study, deep red emitting Mg2TiO4:Mn4+ phosphor ceramics were synthesized by the high temperature solid-state reaction method. The ceramics can be excited by the 465 nm blue light and had a narrow emission with a full width at half maximum (FWMH) value of 31 nm. The peak wavelength was located at 658 nm, which matched the demanded wavelength for photosynthesis. The crystal field strength (Dq) and the Racah parameters (B and C) were estimated by Tanabe-Sugano diagram. The thermal conductivity of the Mg2Ti(0.999)O4: 0.001Mn4+ ceramic was 7.535 W/(m·K) at room temperature, which was one order of magnitude higher than that of the traditional packaging method using the silicone gel. A set of phosphor converted LEDs were fabricated by mounting the phosphor ceramics onto the 460 nm blue LED chips and the CIE coordinates can move from the blue region to the purple light region with the thickness of the ceramic increasing. These results indicated that the Mg2TiO4:Mn4+ phosphor ceramic was suitable for plant lighting when combined with a blue LED chip.

Deep-red emitting Mg2TiO4:Mn4+ phosphor ceramics for plant lighting

In this study, deep red emitting Mg2TiO4:Mn4+ phosphor ceramics were synthesized by the high temperature solid-state reaction method. The ceramics can be excited by the 465 nm blue light and had a narrow emission with a full width at half maximum (FWMH) value of 31 nm. The peak wavelength was located at 658 nm, which matched the most efficient wavelength for photosynthesis. The crystal field strength (Dq) and the Racah parameters (B and C) are estimated by Tanabe-Sugano diagram. The thermal conductivity of the ceramics was 7.535 W/(m·K) at room temperature, which was one order of magnitude higher than that of the traditional packaging method using silicone gel. A set of phosphor converted LEDs were fabricated by mounting the phosphor ceramics onto the 460 nm blue LED chips and the CIE coordinates can move from the blue light region to the purple light region with the thickness of the ceramic increasing. These results indicated that the Mg2TiO4:Mn4+ phosphor ceramic was suitable for plant lighting when combined with a blue LED chip.

Intentional modification of the optical spectral response and relative sensitivity of luminescent thermometers based on Fe3+,Cr3+,Nd3+ co-doped garnet nanocrystals by crystal field strength optimization

The relative sensitivity and usable temperature range of Fe3+,Cr3+-based luminescent thermometers can be tuned by modification of the crystal field strength.