Sensitization of Tb3+ and Dy3+ emission in Li4Ca(BO3)2 via energy transfer from Ce3+ and study of energy transfer mechanism

Abstract

Different series of Li4Ca(BO3)2 singly doped with Ce3+, Tb3+ and Dy3+ as well as codoped with Ce3+-Tb3+ and Ce3+-Dy3+ pairs were prepared by a one-step solid state reaction method. Structural, optical and photoluminescence (PL) properties were studied in detail. The powder X-ray diffraction studies confirmed a single-phased structure with an orthorhombic structure (Pnnm). Vibrational modes of the BO3 groups were determined using Fourier Transform Infrared spectra. The band gap value of 4.98 eV was determined from the UV–vis diffuse reflectance spectroscopy data. The PL of the single and codoped systems were investigated in detail. There was a significant quantitiy of spectral overlap between the emission spectrum of the Ce3+ and the excitation spectra of Tb3+/Dy3+, which showed the possibility of energy transfer from the Ce3+ to the Tb3+/Dy3+. Effective sensitization of the Tb3+ and Dy3+ emission was achieved via energy transfer from Ce3+ in the Li4Ca(BO3)2. The energy transfer mechanism revealed that Ce → Tb energy transfer occured via an electric quadrupole-quadrupole interaction, whereas Ce → Dy energy transfer occured via amn electric dipole-dipole interaction. The prepared materials can act as a strong candidate for near-ultraviolet light emitting diodes and display applications.