2 research outputs found
Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn<sup>4+</sup> Luminescence in the Double Perovskites, Ba<sub>2</sub><i>B</i>TaO<sub>6</sub> (<i>B</i> = Y, Lu, Sc)
The spectroscopic properties of the Mn4+ ion
are investigated
in the series of isostructural double perovskite compounds, Ba2BTaO6 (B = Y,
Lu, Sc). A comparison of these properties highlights the influence
of covalent bonding within the perovskite framework and the degree
of order between the B3+–Ta cations on the energy
and intensity of the Mn4+2E → 4A2 emission transition (R-line). These two parameters of the
emission spectrum are of importance for practical application since
they determine the phosphor luminous efficacy. The influence of covalent
bonding within the corner shared BO6/2 and TaO6/2 perovskite framework on the energy of the R-line energy is investigated.
From the spectroscopic data, we have derived information on the influence
of the degree of order between the B3+ and Ta5+ cations on the intensity of the R-line. The lowest energy and the
highest intensity of the R-line are found in the double perovskite,
Ba2ScTaO6. The purpose of this work is to propose
for first time an explanation of these effects in the considered double
perovskites. The obtained results are useful guidelines for practical
improvement and tuning of key parameters of phosphors to the desired
values
High Light Yield of Sr<sub>8</sub>(Si<sub>4</sub>O<sub>12</sub>)Cl<sub>8</sub>:Eu<sup>2+</sup> under X‑ray Excitation and Its Temperature-Dependent Luminescence Characteristics
In this work, we first investigate
the relationship between temperature
and lattice parameters by means of Rietveld refinement and then demonstrate
its impact on the luminescence peak position of Eu<sup>2+</sup> in
Sr<sub>8</sub>(Si<sub>4</sub>O<sub>12</sub>)ÂCl<sub>8</sub>. It is
found that with increases in temperature, lattice expansion takes
place without significant distortion of the coordination around Eu<sup>2+</sup>. As a result, the crystal field splitting of the Eu<sup>2+</sup> 5d state decreases. At the same time, with the experimental
data of the full width at half-maximum of Eu<sup>2+</sup> emission
at different temperatures and the infrared spectrum, the effective
phonon frequency is evaluated and the main vibration motions are determined
using first-principles calculation. Due to the high light yield under
X-ray excitation and the excellent thermal stability of luminescence
intensity and decay, a further optimized sample Sr<sub>7.7</sub>Eu<sub>0.3</sub>(Si<sub>4</sub>O<sub>12</sub>)ÂCl<sub>8</sub> could be a
potential scintillation material