Recent research results :
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| Improved photoluminescence and afterglow of CaTiO3:Pr3+ by ammonia treatment |
| Songhak Yoon, Eugenio H. Otal, Alexandra E. Maegli, Lassi Karvonen, Santhosh K. Matam, Stefan Riegg, Stefan G. Ebbinghaus, Juan C. Fallas, Hans Hagemann, Bernhard Walfort, Simone Pokrant and Anke Weidenkaff |
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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:Pr3 by XANES. Raman spectroscopy showed that the local crystal structure becomes highly symmetric when the powders are ammonolyzed at 400 °C. Rietveld refinement of powder X-ray diffraction data revealed that the samples ammonolyzed at 400 °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 °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 °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. |
| Optical Materials Express, 3 2 , 2013 , p248 -259 |
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