In this work, we report on the determination of the infrared Yb3+ → Tm3+ energy transfer efficiency in YF3:Yb3+/Tm3+ nanocrystals through the study of Yb3+ dynamics. The obtained results are compared to those previously reported in macrocrystals to analyze possible changes related to size reduction. Luminescence lifetimes are much shorter in the nanoparticles than in…
A procedure for the synthesis of multifunctional europium(III)-doped gadolinium(III) fluoride (Eu:GdF3) nanoparticles (85 nm) with quasispherical shape by precipitation at 120 °C from diethylene glycol solutions containing lanthanide chlorides and an ionic liquid (1-Butyl, 2-methylimidazolium tetrafluoroborate) as fluoride source has been developed. These nanoparticles were polycrystalline and crystallized into a hexagonal structure, which is unusual…
Er-doped LaPO4 microspheres have been synthesized by spray pyrolysis and the near infrared (NIR) properties have been characterized. It has been found that, following an adequate post-annealing treatment, the emission properties are remarkably improved. The NIR luminescence intensity is highly enhanced and its decay time increases to a value almost coincident with the reported radiative…
A facile solvothermal route has been developed for the preparation of tetragonal europium-doped yttrium orthovanadate nanoparticles (Eu:YVO4) and is based on a homogeneous precipitation reaction at 120 °C from solutions of rare earth precursors (yttrium acetylacetonate and europium nitrate) and sodium orthovanadate in ethylene glycol or ethylene glycol/water mixtures. The nature of the solvent has…
Europium-doped calcium hydroxyapatite and fluoroapatite nanophosphors functionalized with poly(acrylic acid) (PAA) have been synthesized through a one-pot microwave-assisted hydrothermal method from aqueous basic solutions containing calcium nitrate, sodium phosphate monobasic, and PAA, as well as sodium fluoride in the case of the fluoroapatite particles. In both cases a spindlelike morphology was obtained, resulting from an…
Homogeneous monoclinic GdPO4 particles composed of three intersecting lance-shaped crystals forming a penetration twin have been synthesized following a very restrictive, simple, and fast (10 min) method consisting of the hydrothermal reaction of gadolinium acetylacetonate with H3PO4 in a mixture of ethylene glycol and water at 180 °C. Slightly increasing the amount of water in…
A simple and fast (7 min) procedure for synthesis of gadolinium phosphate nanocubes (edge = 75 nm) based on the microwave-assisted heating at 120 °C of gadolinium acetylacetonate and phosphoric acid solutions in buthylene glycol is reported. These nanocubes were highly crystalline and crystallized into a tetragonal structure, which has not been ever reported for…
High resolution synchrotron powder XRD, 89Y CPMG NMR, and 139La MAS NMR spectroscopy have been applied to eventually draw the phase diagram of the La2Si2O7–Y2Si2O7 system. The diagram presents a solid solubility region of G-(La,Y)2Si2O7, which extends to the La0.9Y1.1Si2O7 composition at any temperature of this study. Compositions richer in Y show two-phase domains, with…
Phase transitions in LaYSi 2O 7 have been investigated as a function of temperature using XRD, NMR and TEM. Previously described empirical crystal structure guidelines based on average cation radius in rare-earth RE 2Si 2O 7-type disilicates predict a stable tetragonal A-LaYSi 2O 7 polymorph at temperatures below 1500°C. This study demonstrates that A-LaYSi 2O…
Aluminum incorporation into TiO 2 has been studied in the TiO 2-Al 2O 3 system as a function of pressure at temperatures of 900 and 1300 °C using commercial Al 2TiO 5 nanopowder as starting material. A new orthorhombic TiO 2 polymorph with the CaCl 2 structure has been observed in the recovered samples synthesized…