Dependence of Er3+ blue up-conversion on TiO2 contents in SiO2–TiO2 sol–gel powder

The TiO2 content was changed from low to high concentration (5–70% molar) in binary erbium doped SiO2–TiO2 powder samples produced by the sol–gel method. Three pumping wavelengths 532, 979 and 1532 nm, were used to study the blue up-conversion emission and its dependency on the titanium dioxide content. Two erbium concentrations were considered, at 2% and 10% molar. The titanium dioxide content affects the cluster formation, so at low erbium concentration and pumping at 532 nm, the blue and red emissions were enhanced as the TiO2 content increased. However, at high erbium concentration and exciting at 979 and 1532 nm those emissions were quenched as the titanium dioxide was increased.