Optimized microwave assisted synthesis of La2(WO4)3:Tb3+ phosphors and analysis of photoluminescence behavior

NUV/blue LED excitable green emitting terbium doped lanthanum tungstate nanophosphors were successfully synthesized via optimized microwave assisted co–precipitation technique for the first time. Powder XRD analysis confirms that the nanophosphor have monoclinic structure and belongs to space group C2/c. FTIR spectrum identified the characteristic vibrational modes of tungstate group. The chemical composition of the sample was confirmed with the help of EDS technique. Thermogravimetric analysis (TGA) ascertained the outstanding thermal stability of the prepared sample. The strong and wide charge transfer band in the excitation spectrum clearly demonstrates the efficient energy transfer from the host matrix to the terbium ion. This broad band allows for NUV excitation, and the sharp peak at 487 nm indicates that blue LED sources can also be used for excitation. The presence of prominent peak at 543 nm in the emission spectrum, due to 5D4→7F5 transition irrespective of the excitation wavelength, uplifts terbium doped lanthanum tungstate to the group of excellent green emitting phosphors. Decay curves shows single exponential nature and fluorescence life time was obtained. The small value of decay time implies that the synthesized material is suitable for display applications. The calculated CIE chromaticity co–ordinates are close to green emitting phosphors. Thus, terbium doped lanthanum tungstate phosphors are potential phosphors with green emission for WLED applications.