Increased Loading of Eu3+ Ions in Monazite LaVO4 Nanocrystals via Pressure-Driven Phase Transitions

The concentration of Eu3+ ion/dopant in the LaVO4 monazite nanocrystal phase cannot be increased by the conventional synthetic procedures. We demonstrate a unique three-step methodology to increase the doping concentration of Eu3+ in the LaVO4 monazite nanocrystals. In the first step, Eu3+ is doped (10%) in the zircon LaVO4 nanocrystal phase, which does not have a limitation in terms of Eu3+ ion loading. In the second step, high pressure (5 GPa) is utilized to transform the zircon crystal phase to the monazite phase. In the third step, the pressure is brought back to the atmospheric level, wherein it is observed that the monazite crystal phase is retained in its metastable phase with the 10% Eu3+ ion doping concentration. The phase transitions have been characterized via electrical resistivity data, XRD, Raman spectroscopy, fluorescence spectroscopy, TEM, and density functional simulations.