Effect of the Er3+ Co-dopant on the Green Upconversion Emission of LaSr2AlO5:Yb3+ Phosphors


C.R García

This work presents the structural, morphological and optical properties of
LaSr2AlO5:Yb3+,Er3+ phosphors (LSA:Yb,Er) synthesized by a combustion
method. The Yb3+ concentration was kept constant at 2 mol.%, while the Er3+
concentration changed from 0.2 mol.% to 6 mol.%. X-ray diffraction measurements
revealed that all the LSA:Yb,Er phosphors presented a pure
tetragonal phase. Scanning electron microscopy images show that LSA:Yb,Er
phosphors increased their size as the Er3+ concentration increases (from
1.95 lm for Er3+ concentrations< 1 mol.% to 2.3 lm for Er3+ content in the
range of 1 £ x< 6 mol.%,). In addition, the phosphors presented oval-like and
quasipherical shapes for Er3+ content £ 1 mol.%. When the Er3+ concentrations
are> 1 mol.%, the LSA:Yb,Er phosphors present a notorious increase of
conglomeration, and the particles had irregular morphologies. According to
luminescence measurements, the LSA:Yb,Er phosphors present a green
luminescence centered at 549 nm (kexc = 968 nm). The strongest green emission
was observed for an Er3+ concentration of 1 mol.%, above this concentration,
the green emission intensity decreases due to an excess of OH and
carbonate groups on the surface of LSA:Yb,Er phosphors, as confirmed by the
FTIR spectra. Moreover, the CIE coordinates for the green emission were
tuned with the Er3+ concentration. These results suggest that LSA host could
be a good candidate to produce upconversion emission when doped with rare
earths, which could be attractive for the development of lighting sources.

Artículo-CERG 5 2018