ABSTRACT
This paper reports the effect of incorporation of Yb3+ions on the frequency downconversion luminescence and thermal properties of triply ionised Ho3+doped zinc tellurite (TZ) glasses. The photoluminescence spectra of both the Ho3+/Yb3+doped and codoped glasses have been recorded and observed a green emission band corresponding to the5F4,5S2â5I8(â¼550 nm) transition upon various excitations. In the downconversion (DC) emission process, the back energy transfer (BET) mechanism from Ho3+ions to Yb3+ions has also been explored. The colour emitted in the downconversion process is found to be non-tunable at different excitations. Thus, the Ho3+:TZ glass can be utilised for non-colour tunable optical devices under various UV excitations. Also the glass transition (Tg) and crystallisation (Tc) temperatures have been measured for both the doped and codoped glasses and found to be increased in the codoped glass. The singly Ho3+ions doped TZ glass shows better optical downconversion and glass forming ability.
ABSTRACT
Lithium-doped vanadates (V2-xLixO5-δ (0.15 ≤ x ≤ 0.30)) are synthesized by melt-quench method. The physical, structural, optical, thermal and conducting properties of as-quenched samples are investigated using various experimental techniques to study their suitability for electrolyte in battery/solid oxide fuel cell application. X-ray diffraction (XRD) patterns confirm the formation of three different crystalline phases. FTIR and Raman spectra indicate that the doping of Li2O into V2O5 leads to a transition from VO5 into VO4 structural unit. The optical diffused reflectance spectra revealed that the optical band gap (Eg) decreases from 2.2 to 2.08 eV while Urbach energy (EU) increases (0.31-0.41 eV) with the addition of Li2O content in place of vanadium. The thermal stability is studied by thermogravimetric analyser (TGA). The DC conductivity of the present samples is increased from 0.08 to 0.12 Scm-1 at 450 °C with Li2O doping. These materials can be used as electrolyte for battery/solid oxide fuel cell due to their good conductivity (~0.12 Scm-1) at 450 °C.
