Bright red luminescence and energy transfer of Pr3+-doped (Ca,Zn) TiO3 phosphor for long decay applications

A simple and unique method of producing intense red-emitting (Ca, Zn) TiO3 : Pr3+ (CZT : Pr) phosphor with longer decay characteristics is presented. A 1 : 1 molar mixture of H3BO3 and NH4F was identified to be a better fluxing agent and charge compensator in promoting a highly crystalline phase of ( Ca, Zn) TiO3 that in turn favoured the bright red luminescence from Pr3+ ions. It is also observed that addition of ZnO up to 20 mol% to CaTiO3 crystal system incremented the Pr3+ luminescence by several orders and extended its dark persistence time for > 15 min (for a dark-adapted human eye). Further studies indicated that strong red emission is located at similar to 612 nm, which is due to the efficient energy transfer from band gap absorption of CZT to Pr3+ ions. Since the band width is narrow (FWHM similar to 27 nm) and the emission peak is close to the 'ideal red' site of the CIE chromaticity diagram, the phosphor has immense potential for many display-related long decay (LD) applications. Other chemical parameters that affect brightness and observed LD of CZT : Pr phosphor such as the amount of flux, reaction atmosphere, sintering temperature, stoichiometric excess of one or more constituents and amount of dopant were also studied and optimized. X-ray analysis, morphological observations and charge compensation studies revealed some notable features of CZT : Pr LD phosphor.