Hydrothermal formation of luminescent nanoparticles based on zirconia and europium niobate

Abstract

Luminescent nanoparticles based on zirconia (ZrO₂) and europium niobate (Eu₃NbO₇) were directly formed as a single phase of structure corresponding to cubic phase from the precursor solutions of NbCl₅, ZrOCl₂, and EuCl₃ under mild hydrothermal conditions at temperatures more than 180°C. The lattice parameter corresponding to cubic phase decreased with increase in the concentration of ZrO₂. The optical band gap of the nanoparticles with composition 50 and 90 mol % ZrO₂ in the ZrO₂ − 1/4(Eu₃NbO₇) system was 3.5 and 3.6 eV, respectively. The nanoparticles can be excited by ultraviolet light 395 nm (f–f transition) and emit orange (590 nm) and red light (610 nm) corresponding to Eu³⁺ from ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, respectively. The photoluminescence intensity of the sample containing larger amount of ZrO₂ was superior to that of the sample, 50 mol % ZrO₂.