Structure–property relations in hexagonal and monoclinic BiPO₄:Eu³⁺ nanoparticles synthesized by polyol-mediated method

Hexagonal BiPO₄·xH₂O and Bi₀.₉₅Eu₀.₀₅PO₄·xH₂O nanoparticles were synthesized by a polyol-mediated method employing diethylene glycol. The powder X-ray diffraction revealed the phase purity and isostructural nature of both undoped and Eu³⁺-doped BiPO₄. The monoclinic Bi₀.₉₅Eu₀.₀₅PO₄ was obtained by heating the hexagonal Bi₀.₉₅Eu₀.₀₅PO₄·xH₂O at 600 °C. The microscopical characterization revealed the formation of nanocrystalline materials. Water molecules present in the bismuth precursor favoured the formation of hexagonal phase at low temperature. The role of DEG molecules in arresting the particle growth during the phase transformation of Bi₀.₉₅Eu₀.₀₅PO₄ from hexagonal to monoclinic was observed. The synthesized materials were characterized using different spectroscopic techniques such as FT-IR, Raman, ³¹P MAS-NMR, DRUV-Vis and PL. The difference in the crystal structures and symmetries is clearly reflected in the spectral results of hexagonal and monoclinic Bi₀.₉₅Eu₀.₀₅PO₄. The structure-property relations were studied to derive its importance from both fundamental and technological aspects.