Precursor technology for the production of white and color phosphors based on Al2O3:Ln (Ln=Eu3+, Tb3+ or Eu3+ /Tb3+)

Al(1-x)Ln(x)(OH)(HCOO)(2) (Ln = Eu3+, Tb3+ or Eu3+/Tb3+) precursors were synthesized and used as starting reagents for the preparation of white and color luminescent materials. The X-ray powder diffraction data, Infrared, Raman spectra and thermal analysis of precursors are discussed in detail. Vibrational spectroscopy corroborates the X-ray diffraction results, Al(1-x)Ln(x)(OH)(HCOO)(2) crystallize in the monoclinic system. Thermolysis of Al(1-x)Ln(x)(OH)(HCOO)(2 )precursors in helium atmosphere and in air at temperatures below 700 degrees C allows one to obtain poorly crystallized Al2O3:Ln samples. The temperature required for the synthesis of gamma-(Al(1-x)Ln(x))(2)O-3 solid solutions is equal to 900 degrees C. Complete characterization of the products of thermolysis of precursors was performed using X-ray powder diffraction, Al-27 MM NMR, optical absorption and luminescence. The presence of europium and terbium ions in the aluminum oxide leads to the stability of the gamma-phase, i.e. inhibits the formation of alpha-Al2O3. The europium and terbium codoped Al2O3 prepared by thermolysis of precursors in helium atmosphere and in air exhibits luminescence close to white light under UV excitation. The optimal concentration of dopants, Eu3+ and Tb3+ ions, in the gamma-Al2O3 hosts with while-blue emission makes it possible to improve the CIE color coordinates and obtain white luminescence.