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

Abstract

Hexagonal BiPO₄·xH₂O and Bi_0.95Eu_0.05PO₄·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 Bi_0.95Eu_0.05PO₄ was obtained by heating the hexagonal Bi_0.95Eu_0.05PO₄·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 Bi_0.95Eu_0.05PO₄ 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 Bi_0.95Eu_0.05PO₄. The structure-property relations were studied to derive its importance from both fundamental and technological aspects.