Phase stabilization and optical response in the ultraviolet range, due to terbium concentration in hafnium oxide nanoparticles.

This work reports the influence of terbium trivalent ions on growing kinetics and the phase in hafnium oxide nanoparticles, as well as response to radiation in the range from 256 to 286. The nanoparticles were obtained by the hydrothermal route maintaining the temperature constant and varying the reaction time and the terbium concentration. The results show a gradual change in the phase with the concentration of terbium trivalent ions, going from the monoclinic phase, present at low concentrations, to the tetragonal phase, which appears from dopant concentrations greater than 5% at., increasing in amount with concentration of dopant. These phases appear as two perfectly defined morphologies. Furthermore, there is a significant change in radiative lifetimes when the tetragonal phase appears.

Thermally coupled energy levels of Eu 3+ within the BaHfO3 matrix, excited with UV radiation.

The present work reports the study of the thermally coupled energy levels of the trivalent europium ion in the barium hafnate matrix, in the temperature range of 289.7-323.8 K, through the application of ultraviolet radiation. Barium hafnate doped with 1, 3, and 5 atomic % trivalent europium ion was synthesized by the hydrothermal route, using chlorides as precursor elements. X-ray diffraction analysis indicates that the material crystallized in the perovskite cubic phase of barium hafnate, according to diffraction card file number #24-0102. Using high-resolution transmission electron microscopy, it was observed that the obtained crystals have an average size of 10 nm. From the photoluminescent analysis at room temperature, it was found that the sample doped with 3.0% atomic of trivalent europium displayed with the highest luminescent emission, while the photoluminescent analysis as a function of temperature showed that the bands associated with the 5D0 → 7FJ (J = 1,2,3,4) transitions have a strong dependence on temperature in the physical range.

Luminescent behavior of Eu3+ doped BaHfO3 perovskite ceramic under UV radiation.

In this paper, luminescent properties of Europium trivalent ion in the matrix with unbalanced charge of barium hafnate under UV radiation, with special emphasis on the 5D0 → 7F0 transition are reported. The synthesis was conducted by the hydrothermal route at 200 °C with a reaction time of 90 min using chlorides as raw materials. In order to determinate the luminescent quenching concentration, the samples were doped with different amounts of Europium trivalent ions being the sample doped with 1 and 3% at of Eu3+ which shows the highest luminescent emission. X-ray diffraction analysis showed that the material crystallize in the cubic perovskite structure with space group Pm-3m. The Energy Dispersive Spectroscopy (EDS) shows there are not elements other those that Ba, Hf, O and Eu in the synthesized material. Photoluminescent emission spectra show peaks of emission associated with the 5D0 → 7FJ (J = 0,1,2,3,4) transitions, characteristics of europium ion. The 5D0 → 7F0 transition centered at 580 nm showed an unusual great intensity when it was excited with the wavelength associated with the charge transfer band (272 nm). Finally the decay time was measured in the 5D0 → 7FJ (J = 0,1,2,3,4) transitions using the sample doped with Eu3+ (3% at).