CaMoO4: Ho3+-Yb3+-Mg2+ upconverting phosphor for application in lighting devices and optical temperature sensing

The CaMoO4 phosphors codoped with Ho3+, Yb3+, Mg2+ ions, synthesized by chemical coprecipitationroute and characterized structurally by X- ray diffraction analysis have shown the tetragonal phase of CaMoO4. The codoping with Mg2+ ion causes shrinkage in the lattice dimension due to substitutional effect. For the investigation of particle size and the surface morphology of the prepared material the high resolution transmission electron microscopy ( HRTEM) and field emission scanning electron microscopy( FESEM) analysis have been performed respectively. The prepared phosphor powders upon excitationwith 980 nm laser radiation give intense red ( 660 nm) and green ( 545 nm) UC emissions along with weakblue ( 460 nm, 489 nm) and near infrared ( 756 nm) emission bands. The enhancement in the upconversion( UC) emission intensity has been observed due to codoping with Mg2+ ions. The lifetime corresponding to F-5(4), S-5(2) -> I-5(8), F-5(5) -> I-5(8) transitions have been analyzed to cross- check the UC mechanism. The effect ofvariation of pump power and also the external temperature on the blue emission bands correspondingto the K-3(8) -> I-5(8) and F-5(3) -> I-5(8) transitions respectively have been monitored to investigate the sensingproperty of the phosphor. (C) 2015 Elsevier B.V. All rights reserved.