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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. Developing innovative materials for reduced energy consumption in phosphor converted white light-emitting diodes remains a challenge. Here, the authors report a narrow band red-emitting oxonitride material with a highly symmetrical Sr2 + coordination for energy efficient white light-emitting diodes.

Layered crystalline materials that consist of transition metal atoms on a kagome network have emerged as a versatile platform for the study of unusual electronic phenomena. For example, in the vanadium-based kagome superconductors AV3Sb5 (where A can stand for K, Cs or Rb), there is a parent charge density wave phase that appears to simultaneously break both the translational and rotational symmetries of the lattice. Here we show a contrasting situation, where electronic nematic order—the breaking of rotational symmetry without the breaking of translational symmetry—can occur without a corresponding charge density wave. We use spectroscopic-imaging scanning tunnelling microscopy to study the kagome metal CsTi3Bi5 that is isostructural to AV3Sb5 but with a titanium atom kagome network. CsTi3Bi5 does not exhibit any detectable charge density wave state, but a comparison to density functional theory calculations reveals substantial electronic correlation effects at low energies. In comparing the amplitudes of scattering wave vectors along different directions, we discover an electronic anisotropy that breaks the sixfold symmetry of the lattice, arising from both in-plane and out-of-plane titanium-derived d orbitals. Our work uncovers the role of electronic orbitals in CsTi3Bi5, suggestive of a hexagonal analogue of the nematic bond order in Fe-based superconductors.Electronic nematic order as a distinct phase in kagome materials without any entanglement with charge density wave or charge stripe order has not been detected. Now, it is observed in a titanium-based kagome metal.

Na1.36(Si0.86Ga0.14)2As2.98 and Li1.5Ga0.9Si3.1As4 were synthesized by heating mixtures of the elements at 950 °C. The crystal structures were determined by single crystal X-ray diffraction (Na1.36(Si0.86Ga0.14)2As2.98: I41/a, Z = 100, a = 19.8772(4) Å, c = 37.652(1) Å; Li1.5Ga0.9Si3.1As4: C2/c, Z = 8, a = 10.8838(6) Å, b = 10.8821(6) Å, c = 13.1591(7) Å). Na1.36(Si0.86Ga0.14)2As2.98 crystallizes similar to NaSi2P3 with interpenetrating networks of vertex-sharing T4 and T5 supertetrahedra. Gallium substitution at the silicon sites increases the charge of the cluster network, which is compensated for by a 36% higher sodium content. Since in contrast to NaSi2P3, all sodium sites are now fully occupied, there is no significant ion mobility, as indicated by 23Na-NMR. Consequently, the total sodium-ion conductivity of Na1.36(Si0.86Ga0.14)2As2.98 amounts to only 1.6(1) × 10−7 S cm−1 and is therefore three orders of magnitude lower than in NaSi2P3. Li1.5Ga0.9Si3.1As4 crystallizes in a new structure type with layers of edge-sharing (Si1−xGax)As4 tetrahedra alternating with layers that contain infinite Sin zigzag chains. Lithium ions reside in channels between the chains, and thus, the structure does not provide three dimensional pathways for ion conduction and the measured total Li-ion conductivity amounts to only 1.3(1) × 10−7 S cm−1.

Three members of the homologous series of manganese oxyselenides with the general formula La2n+2MnSen+2O2n+2 (n = 0–2) have been synthesized in a NaI/KI flux and characterized by single-crystalX-raydiffraction,powderX-raydiffractionandmagneticmeasurements. Thestructures consist of chains of edge-sharing MnSe4O2-octahedra along the b-axis which are linked together along the a-axis by edge-sharing OLa4- and/or OLa3Mn-tetrahedra forming infinite ribbons of increasing width. mC-La2MnSe2O2 (Pb2HgCl2O2-type, C2/m, a = 11.6621(5) Å, b = 3.9719(1) Å, c = 7.2049(3) Å, β = 121.655(2)◦) represents a new polymorph of this compound. La4MnSe3O4 (P2/m, a = 9.0055(4) Å, b = 4.0186(1) Å, c = 7.1946(3) Å, β = 109.715(2)◦) and La6MnSe4O6 (C2/m, a = 24.760(2) Å,b = 4.0359(3)Å,c=7.1850(6)Å, β =104.162(3)◦)exhibitnewstructuretypes. Magnetic measurements suggest antiferromagnetic order of the moments below about 15 K with effective magnetic moments of 5.53(1), 5.99(1) and 6.01(1) µB per formula unit for n = 1, 2 and 3, respectively.

Intermetallic compounds play an extraordinary role in daily life for construction materials and well-defined functions that are based on their specific chemical and physical properties, e.g. magnetism and superconductivity. High-tech materials are meanwhile indispensable in our technology-driven information society. The Periodic Table comprises more than 80 metallic elements which offer an incredible potential for formation of binary, ternary and even multinary intermetallic compounds with peculiar crystal structures and properties. The present textbook introduces into the basics of intermetallic chemistry with an emphasis on crystal chemistry and selected chemical and physical properties.

Na[sub.1.36] (Si[sub.0.86] Ga[sub.0.14] )[sub.2] As[sub.2.98] and Li[sub.1.5] Ga[sub.0.9] Si[sub.3.1] As[sub.4] were synthesized by heating mixtures of the elements at 950 °C. The crystal structures were determined by single crystal X-ray diffraction (Na[sub.1.36] (Si[sub.0.86] Ga[sub.0.14] )[sub.2] As[sub.2.98] : I 4[sub.1] /a , Z = 100, a = 19.8772(4) Å, c = 37.652(1) Å; Li[sub.1.5] Ga[sub.0.9] Si[sub.3.1] As[sub.4] : C 2/c , Z = 8, a = 10.8838(6) Å, b = 10.8821(6) Å, c = 13.1591(7) Å). Na[sub.1.36] (Si[sub.0.86] Ga[sub.0.14] )[sub.2] As[sub.2.98] crystallizes similar to NaSi[sub.2] P[sub.3] with interpenetrating networks of vertex-sharing T4 and T5 supertetrahedra. Gallium substitution at the silicon sites increases the charge of the cluster network, which is compensated for by a 36% higher sodium content. Since in contrast to NaSi[sub.2] P[sub.3] , all sodium sites are now fully occupied, there is no significant ion mobility, as indicated by [sup.23] Na-NMR. Consequently, the total sodium-ion conductivity of Na[sub.1.36] (Si[sub.0.86] Ga[sub.0.14] )[sub.2] As[sub.2.98] amounts to only 1.6(1) × 10[sup.−7] S cm[sup.−1] and is therefore three orders of magnitude lower than in NaSi[sub.2] P[sub.3] . Li[sub.1.5] Ga[sub.0.9] Si[sub.3.1] As[sub.4] crystallizes in a new structure type with layers of edge-sharing (Si[sub.1−x] Gax )As[sub.4] tetrahedra alternating with layers that contain infinite Sin zigzag chains. Lithium ions reside in channels between the chains, and thus, the structure does not provide three dimensional pathways for ion conduction and the measured total Li-ion conductivity amounts to only 1.3(1) × 10[sup.−7] S cm[sup.−1] .

Intermetallic compounds play an extraordinary role in daily life for construction materials and well-defined functions that are based on their specific chemical and physical properties, e.g. magnetism and superconductivity. High-tech materials are meanwhile indispensable in our technology-driven information society. The Periodic Table comprises more than 80 metallic elements which offer an incredible potential for formation of binary, ternary and even multinary intermetallic compounds with peculiar crystal structures and properties. The present textbook introduces into the basics of intermetallic chemistry with an emphasis on crystal chemistry and selected chemical and physical properties.

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 Al O N ]:Eu 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 Al O N ]:Eu 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.