New self charge compensating perovskite type red phosphors prepared via ball milling process for pc-white light emitting diode applications

Abstract

New self charge compensating red emitting perovskite type phosphors, Na(1+x)Ca(1-2x)TiNbO6:x Eu3+ were prepared by a high energy ball milling method and subsequent calcination process in the temperature range 1000–1200 °C. Their structural, morphological and optical properties were studied by advanced characterization tools. The X-ray diffraction analysis confirms the formation of orthorhombic type structure with a space group Pnma. These phosphors exhibit intense red emission due to forced electric dipole transition, 5D0→7F2 under near UV (395 nm) and blue (463 nm) excitations. The dominant red emission with high asymmetry ratio further evidences the occupancy of Eu3+ at the non-centrosymmetric A site of the perovskite. The high concentration quenching (20 mol%.) is observed in the system due to layered ordering of the A site cations occupied by Eu3+ion also. The photoluminescence properties of these phosphors were optimized with calcination temperature. Morphological observation reveal increase in the grain size of the phosphor particles with calcination temperature. The optimum phosphor properties were found at 1100 °C and beyond that quenches the luminescence. Also the comparison of photoluminescent emission of commercial red phosphor Y2O3: Eu3+with our prepared optimized phosphor Na(1.2)Ca(0.8)TiNbO6: 0.2Eu3+ (1100 °C) was carried out. We got very good emission intensity in comparison with the commercial one. The calculated CIE color co-ordinates and Correlated Color Temperature are (0.65, 0.33) and 2799 K respectively, also we got excellent color purity value of 94%. The obtained results suggest that the developed red phosphors are potential candidates for white light emitting diode (WLED) applications.