Improved photoluminescence and afterglow of CaTiO3:Pr3+ by ammonia treatment

YOON, SONGHAK; OTAL, EUGENIO H.; MAEGLI, ALEXANDRA E.; KARVONEN, LASSI; MATAM, SANTHOSH K; RIEGG, STEFAN; EBBINGHAUS, STEFAN G; FALLAS, JUAN C.; HAGEMANN, HANS; WALFORT, BERNHARD; (POKRANT, SIMONE; WEIDENKAFF, ANKE

OPTICAL MATERIALS EXPRESS

OPTICAL SOC AMER

Año: 2013 vol. 3 p. 248 - 259

2159-3930

The phosphor CaTiO3:Pr3+ was synthesized via a solid-state reaction in combination with a subsequent annealing under flowing NH3. Comparatively large off-center displacements of Ti in the TiO6 octahedra were confirmed for as-synthesized CaTiO3:Pr-3 by XANES. Raman spectroscopy showed that the local crystal structure becomes highly symmetric when the powders are ammonolyzed at 400 degrees C. Rietveld refinement of powder X-ray diffraction data revealed that the samples ammonolyzed at 400 degrees C have the smallest lattice strain and at the same time the largest average Ti-O-Ti angles were obtained. The samples ammonolyzed at 400 degrees C also showed the smallest mass loss during the thermal re-oxidation in thermogravimetric analysis (TGA). Enhanced photolumincescence brightness and an improved decay curve as well as the highest reflectance were obtained for the samples ammonolyzed at 400 degrees C. The improved photoluminescence and afterglow by NH3 treatment are explained as a result of the reduced concentration of oxygen excesses with simultaneous relaxation of the lattice strain.