Effect of solvents on the morphology and optical properties of rare-earth ions doped BiOBr 3D flower-like microparticles via solvothermal method

Eu³⁺ or Sm³⁺ ions individually doped bismuth oxybromide (BiOBr) phosphors with three-dimensional flower-like microsphere morphology were prepared by a solvothermal method. The variation of ethylene glycol and ethanol concentrations affected the surface morphology of microparticles, which was investigated by field-emission scanning electron microscope images. The crystallinity and phase formation of BiOBr microspheres were analyzed by X-ray diffraction patterns, confirming the tetragonal phase with space group of P4/nmm (129). The photoluminescence (PL) properties were measured for the Eu³⁺or Sm³⁺ ions single doped BiOBr phosphors. From the temperature-dependent PL emission spectra, the activation energies of the Eu³⁺or Sm³⁺ ions single doped BiOBr samples were estimated. The PL emission spectra of the BiOBr:Eu³⁺ phosphors exhibited a reddish orange emission at 616 nm due to the characteristic ⁵D₀ → ⁷F₂ electronic transition at a blue excitation wavelength of 464 nm. The Sm³⁺ ions doped BiOBr phosphors revealed an emission at 603 nm of wavelength under the excitation wavelength of 408 nm. Also, the PL emission intensities of the optimized BiOBr:Eu³⁺ and BiOBr:Sm³⁺ samples were increased after calcination at 500 °C.