Crystal structure and morphology evolution in the LaXO3, X = Al, Ga, In nano-oxide series. Consequences for the synthesis of luminescent phosphors

Experimental and Theoretical Study of the Electronic Structures of Lanthanide Indium Perovskites LnInO3

Ternary lanthanide indium oxides LnInO₃ (Ln = La, Pr, Nd, Sm) were synthesized by high-temperature solid-state reaction and characterized by X-ray powder diffraction. Rietveld refinement of the powder patterns showed the LnInO₃ materials to be orthorhombic perovskites belonging to the space group Pnma, based on almost-regular InO₆ octahedra and highly distorted LnO₁₂ polyhedra. Experimental structural data were compared with results from density functional theory (DFT) calculations employing a hybrid Hamiltonian. Valence region X-ray photoelectron and K-shell X-ray emission and absorption spectra of the LnInO₃ compounds were simulated with the aid of the DFT calculations. Photoionization of lanthanide 4f orbitals gives rise to a complex final-state multiplet structure in the valence region for the 4f ⁿ compounds PrInO₃, NdInO₃, and SmInO₃, and the overall photoemission spectral profiles were shown to be a superposition of final-state 4f ^n-1 terms onto the cross-section weighted partial densities of states from the other orbitals. The occupied 4f states are stabilized in moving across the series Pr-Nd-Sm. Band gaps were measured using diffuse reflectance spectroscopy. These results demonstrated that the band gap of LaInO₃ is 4.32 eV, in agreement with DFT calculations. This is significantly larger than a band gap of 2.2 eV first proposed in 1967 and based on the idea that In 4d states lie above the top of the O 2p valence band. However, both DFT and X-ray spectroscopy show that In 4d is a shallow core level located well below the bottom of the valence band. Band gaps greater than 4 eV were observed for NdInO₃ and SmInO₃, but a lower gap of 3.6 eV for PrInO₃ was shown to arise from the occupied Pr 4f states lying above the main O 2p valence band.

Optically and thermally stimulated luminescence characteristics of LaAlO3:Pr3+ beta irradiated

This paper reports on an investigation into the thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL) characteristics of novel luminescent phosphor. A new Pr³⁺-doped, lanthanum aluminate (LaAlO₃)-based luminescent phosphor is developed. Samples of LaAlO₃:Pr³⁺ were irradiated to beta doses, in air, from 0.1Gy up to 50Gy and then were analyzed using both TL and continuous wavelength OSL (CW-OSL) techniques to determine their luminescent characteristics. This phosphor shows a TL glow curve, after its irradiation to beta radiation, with two TL peaks: one located around 160°C and a second at 300°C. CW-OSL response presented a fast decay into the first 20s of blue light stimulation. TL and CW-OSL response as a function of beta radiation dose were linear in the studied dose range. The high sensitivity of the CW-OSL and TL response will make this phosphor suitable for beta radiation detection. Finally, the kinetic parameters of activation energy, frequency factor and kinetic order were analyzed in the TL response using computerized glow curve deconvolution based on general order kinetic model.

Non-contact Mn1−xNixFe2O4 ferrite nano-heaters for biological applications – heat energy generated by NIR irradiation

Effective heat generation achieved on Mn_1−xNi_xFe₂O₄ferrite nano-heaters using NIR light irradiation instead of AC magnetic field.

Precursor directed synthesis--"molecular" mechanisms in the Soft Chemistry approaches and their use for template-free synthesis of metal, metal oxide and metal chalcogenide nanoparticles and nanostructures

This review provides an insight into the common reaction mechanisms in Soft Chemistry processes involved in nucleation, growth and aggregation of metal, metal oxide and chalcogenide nanoparticles starting from metal-organic precursors such as metal alkoxides, beta-diketonates, carboxylates and their chalcogene analogues and demonstrates how mastering the precursor chemistry permits us to control the chemical and phase composition, crystallinity, morphology, porosity and surface characteristics of produced nanomaterials.