2 research outputs found
Crystal Structures and Photoluminescence across the La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>āHo<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> System
It is well-known that when an RE<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> matrix is doped with active lanthanide
ions, it displays promising luminescent responses for optical applications.
The crystalline structure adopted by the silicate matrix as well as
the distribution of the dopants among the available RE crystallographic
sites have important effects on the luminescent yields of these compounds.
The present study is aimed at analyzing the structural behavior as
well as the luminescent properties of Ho<sup>3+</sup>-substituted
La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>. Several compositions across
the La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>āHo<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> system were synthesized using the solāgel
method followed by calcination at 1600 Ā°C. The resulting powders
were analyzed by means of X-ray and neutron diffraction to determine
the phase stabilities across the system. The results indicated a solid
solubility region of G-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> which extends to the La<sub>0.6</sub>Ho<sub>1.4</sub>Si<sub>2</sub>O<sub>7</sub> composition. Compositions richer in Ho<sup>3+</sup> show a two-phase domain (G+Ī“), while Ī“-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> is the stable phase for Ho<sup>3+</sup> contents higher than 90% (La<sub>0.2</sub>Ho<sub>1.8</sub>Si<sub>2</sub>O<sub>7</sub>). Anomalous diffraction data interestingly indicated
that the La<sup>3+</sup> for Ho<sup>3+</sup> substitution mechanism
in the G-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> polymorph
is not homogeneous, but a preferential occupation of Ho<sup>3+</sup> for the RE2 site is observed. The Ho<sup>3+</sup>-doped G-La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> phosphors exhibited a strong green
luminescence after excitation at 446 nm. Lifetime measurements indicated
that the optimum phosphor was that with a Ho<sup>3+</sup> content
of 10%
Crystal Structures and Photoluminescence across the La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>āHo<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> System
It is well-known that when an RE<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> matrix is doped with active lanthanide
ions, it displays promising luminescent responses for optical applications.
The crystalline structure adopted by the silicate matrix as well as
the distribution of the dopants among the available RE crystallographic
sites have important effects on the luminescent yields of these compounds.
The present study is aimed at analyzing the structural behavior as
well as the luminescent properties of Ho<sup>3+</sup>-substituted
La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>. Several compositions across
the La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub>āHo<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> system were synthesized using the solāgel
method followed by calcination at 1600 Ā°C. The resulting powders
were analyzed by means of X-ray and neutron diffraction to determine
the phase stabilities across the system. The results indicated a solid
solubility region of G-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> which extends to the La<sub>0.6</sub>Ho<sub>1.4</sub>Si<sub>2</sub>O<sub>7</sub> composition. Compositions richer in Ho<sup>3+</sup> show a two-phase domain (G+Ī“), while Ī“-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> is the stable phase for Ho<sup>3+</sup> contents higher than 90% (La<sub>0.2</sub>Ho<sub>1.8</sub>Si<sub>2</sub>O<sub>7</sub>). Anomalous diffraction data interestingly indicated
that the La<sup>3+</sup> for Ho<sup>3+</sup> substitution mechanism
in the G-(La,Ho)<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> polymorph
is not homogeneous, but a preferential occupation of Ho<sup>3+</sup> for the RE2 site is observed. The Ho<sup>3+</sup>-doped G-La<sub>2</sub>Si<sub>2</sub>O<sub>7</sub> phosphors exhibited a strong green
luminescence after excitation at 446 nm. Lifetime measurements indicated
that the optimum phosphor was that with a Ho<sup>3+</sup> content
of 10%