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Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al2O3-SiO2 glass. Using optical absorption spectroscopy, we demonstrated that the LSPR band's position and shape can be finely controlled by varying the thermal treatment route. Comprehensive methods including Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy were used to study the glass structure, while computational approaches were used for the theoretical description of the absorption spectra. The obtained results allowed us to suggest a scenario responsible for an abnormal LSPR band broadening that includes a possible interparticle plasmonic coupling effect taking place during the liquid–liquid phase separation of the heat-treated glass. The formation of gold NPs with an ultra-broad LSPR band in glasses holds promise for sensitizing rare earth ion luminescence for new photonics devices. [ABSTRACT FROM AUTHOR]

The local aluminum structure in zeolite mordenite was studied at temperatures up to 1000 K in a vacuum by Al K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The FT analysis of Al K-edge XANES showed a highly distorted tetrahedral coordination of the dehydrated H-mordenite.

The spinel oxide AlV2O4 is a unique material, in which the formation of clusters is accompanied by atomic, charge and orbital ordering and a rhombohedral lattice distortion. In this work a theory of the structural phase transition in AlV2O4 is proposed. This theory is based on the study of the order‐parameter symmetry, thermodynamics, electron density distribution, crystal chemistry and mechanisms of formation of the atomic and orbital structures of the rhombohedral phase. It is established that the critical order parameter is transformed according to irreducible representation k9(τ4) (in Kovalev notation) of the space group. Knowledge of the order‐parameter symmetry allows us to show that the derived AlV2O4 rhombohedral structure is a result of displacements of all atom types and the ordering of Al atoms (1:1 order type in tetrahedral spinel sites), V atoms (1:1:6 order type in octahedral sites) and O atoms (1:1:3:3 order type), and the ordering of dxy, dxz and dyz orbitals. Application of the density functional theory showed that V atoms in the Kagomé sublattice formed separate trimers. Also, no sign of metallic bonding between separate vanadium trimers in the heptamer structure was found. The density functional theory study and the crystal chemical analysis of V—O bond lengths allowed us to assume the existence of dimers and trimers as main clusters in the structure of the AlV2O4 rhombohedral modification. The trimer model of the low‐symmetry AlV2O4 structure is proposed. Within the Landau theory of phase transitions, typical diagrams of possible phase states are built. It is shown that phase states can be changed as a first‐order phase transition close to the second order in the vicinity of tricritical points of the phase diagrams. [ABSTRACT FROM AUTHOR]

The spinel oxide AlV2O4 is a unique material, in which the formation of clusters is accompanied by atomic, charge and orbital ordering and a rhombohedral lattice distortion. In this work a theory of the structural phase transition in AlV2O4 is proposed. This theory is based on the study of the order‐parameter symmetry, thermodynamics, electron density distribution, crystal chemistry and mechanisms of formation of the atomic and orbital structures of the rhombohedral phase. It is established that the critical order parameter is transformed according to irreducible representation k9(τ4) (in Kovalev notation) of the space group. Knowledge of the order‐parameter symmetry allows us to show that the derived AlV2O4 rhombohedral structure is a result of displacements of all atom types and the ordering of Al atoms (1:1 order type in tetrahedral spinel sites), V atoms (1:1:6 order type in octahedral sites) and O atoms (1:1:3:3 order type), and the ordering of dxy, dxz and dyz orbitals. Application of the density functional theory showed that V atoms in the Kagomé sublattice formed separate trimers. Also, no sign of metallic bonding between separate vanadium trimers in the heptamer structure was found. The density functional theory study and the crystal chemical analysis of V—O bond lengths allowed us to assume the existence of dimers and trimers as main clusters in the structure of the AlV2O4 rhombohedral modification. The trimer model of the low‐symmetry AlV2O4 structure is proposed. Within the Landau theory of phase transitions, typical diagrams of possible phase states are built. It is shown that phase states can be changed as a first‐order phase transition close to the second order in the vicinity of tricritical points of the phase diagrams. [ABSTRACT FROM AUTHOR]