Bright red luminescence and energy transfer of Pr³⁺-doped (Ca,Zn)TiO₃phosphor for long decay applications

Abstract

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 ∼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∼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.