Rational Hydrothermal Route to Monodisperse Hf1-xEuxO2-x/2 Solid Solution Nanocrystals

Abstract

Highly dispersed and nearly uniformly sized Hf1-xEuxO2-x/2 (x = 0.05, 0.1, and 0.15) solid solution nanoparticles with particle sizes between 2.2 and 5.2 nm were produced via the hydrothermal treatment of a metal−oleate complex precursor at 200 °C for 6 h. The obtained nanocrystals were characterized by IR, EDX, XRD, Raman scattering, TEM, and PL spectroscopy. It was demonstrated that the proposed synthetic technique led to the formation of a Hf1-xEuxO2-x/2 solid solution with a thermodynamically metastable phase (tetragonal HfO2 phase). Pure HfO2 nanocrystals were rod-like in shape with a monoclinic phase, while the doping of HfO2 by Eu3+ resulted in the nearly spherically shaped nanocrystals. The PL spectroscopy showed significant quenching of Eu3+ 5Do → 7Fn radiative transitions for the as-prepared samples, whereas the annealed sample at 400 °C for 5 h showed clear red luminescence.