Red phosphors AMF6:Mn(4+) (A = Na, K, Cs, Ba, Rb; M = Si, Ti, Ge) have been widely studied due to the narrow red emission bands around 630 nm. The different emission of the zero-phonon line (ZPL) may affect the color rendering index of white light-emitting diodes (WLED). The primary reason behind the emergence and intensity of ZPL, taking KNaSiF6:Mn(4+) as an example, was investigated here. The effects of pressure on crystal structure and luminescence were determined experimentally and theoretically. The increase of band gap, red shift of emission spectrum and blue shift of excitation spectrum were observed with higher applied pressure. The angles of ∠FMnF and ∠FMF(M = Si, Ti, Ge) were found clearly distorted from 180° in MF6(2-) octahedron with strong ZPL intensity. The larger distorted SiF6(2-) octahedron, the stronger ZPL intensity. This research provides a new perspective to address the ZPL intensity problem of the hexafluorosilicate phosphors caused by crystal distortion and pressure-dependence of the luminescence. The efficacy of the device featuring from Y3Al5O12:Ce(3+) (YAG) and KNaSiF6:Mn(4+) phosphor was 118 lm/W with the color temperature of 3455 K. These results reveal that KNaSiF6:Mn(4+) presents good luminescent properties and could be a potential candidate material for application in back-lighting systems.

The success of semiconductor technology is largely ascribed to controlled impacts of strains and defects on the two-dimensional interfacial charges. Interfacial charges also appear in oxide heterojunctions such as LaAlO 3 /SrTiO 3 and (Nd 0.35 Sr 0.65 )MnO 3 /SrTiO 3 . How the localized strain field of one-dimensional misfit dislocations, defects resulting from the intrinsic misfit strains, would affect the extended oxide-interfacial charges is intriguing and remains unresolved. Here we show the atomic-scale observation of one-dimensional electron chains formed in (Nd 0.35 Sr 0.65 )MnO 3 /SrTiO 3 by the condensation of characteristic twodimensional interfacial charges into the strain field of periodically arrayed misfit dislocations, using chemical mapping and quantification by scanning transmission electron microscopy. The strain-relaxed inter-dislocation regions are readily charge depleted, otherwise decorated by the pristine charges, and the corresponding total-energy calculations unravel the undocumented charge-reservoir role played by the dislocation-strain field. This two-dimensionalto-one-dimensional electronic condensation represents a novel electronic-inhomogeneity mechanism at oxide interfaces and could stimulate further studies of one-dimensional electron density in oxide heterostructures.

has been observed to increase from 88 to 94 K with increasing radius of the R ion (r) from 0.98 to 1.12 A. Based on the lattice strains and our dT, /dP data, we have calculated T, for the series of R-123 and compared them with the measured T, . Good agreement between the experimental and the calculated results strongly suggests that the R effect on T, in R-123 originates from the strain-induced charge redistribution between the charge reservoir and the Cu02 plane.While the microscopic mechanism of high-temperature superconductors (HTS) is still elusive, the electronic structure of relevant cuprates has been characterized by a phasediagram of temperature (T) and the carrier concentration (n). This T ndiagra-m shows that the superconductivity occurs in a certain range of n, and the superconducting transition temperature (T,) is approximately a parabolic function of n. From the structural point of view, it is widely believed that the CuOz plane is the principal site for the superconducting activity, and the metal oxide (i.e., MO, where M is Cu, La, Hg, Tl, or Bi serves as a charge reservoir to supply carriers into the CuOz plane. Other structural components such as rare-earth and alkaline elements work as counter cations to stabilize the structure. However, some evidences have shown that the influence of rare-earth elements (R) on T, should not be ignored. For YBa2Cu307 (Y-123), it was demonstrated that the substitution of some magnetic R ions have no significant effect on T, , thus leading to an assumption that the R site in the R-123 structure was electronically isolated from conduction electrons. Although a T, variation in the series of oxygenated R-123 had been noticed by Neumeier, the relatively large scattering in the values of T, made a quantitative analysis difficult. Later, the work by Fernandes et al. with a good control of sample quality showed that the T, value for fully oxygenated Gdi Y BazCu307 decreased linearly with increasing x.This result confirmed a significant R effect on T, in R-123.Very recently, Ramesh and Hedge reported that, based on a calculation of the bond-valence sums for R-123, the valence of the in-plane copper Cu(2) increases with decreasing radius of the R ion (r), implying an increase of carrier concentration in the CuOz plane with decreasing r. Then, the combination of the experimental results of Fernandes et aI. and the calculation of Ramesh and Hedge gives rise to a conclusion that T, can be lower when n is higher in the series of R-123. This conclusion contradicts with the general belief that T, should increase with increasing carrier concentration and raises an interesting issue regarding the relationship between T, and n in these materials. We therefore have performed a systematic measurement of T, and pressure effect of T, for a series of fully-oxygenated R-123 samples with an attempt to delineate the implication of the R effect on T, .In this work, polycrystalline RBazCu307 z with R= Yb, Tm, Ho, Dy, Gd, Sm, and Nd were prepared by the standard solid-state reaction technique....

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Searching for a non-rare-earth-based oxide red-emitting phosphor is crucial for phosphor-converted light-emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited SrAlO:Mn phosphor exhibiting red emission peaked at ∼653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of SrAlO:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of SrAlO were analyzed by density functional theory calculations using the hybrid exchange-correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial β-SiAlON:Eu green phosphor, and SrAlO:Mn red phosphor were evaluated for commercial applications: using the present SrAlO:Mn red phosphor converted LED as a backlighting source.

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