Optical ceramics are finding a strong technological interest in the field of laser and scintillation materials as an alternative to single crystals. The most favourable structural composition is the cubic one; in fact, due to the isotropy of the optical parameters occurring in this case, it is possible to obtain highly transparent bulk materials made of compacted micro - or nano - metric grains. Presently the mostly studied optical ceramics are rare-earth doped Y- and Lu- Aluminium garnets [1, and references therein]. In several cases sintering agents like Si, Mg, Sc, or La are also used. Indeed, it was found that their introduction causes a transparency improvement, accompanied, however, by a deterioration of the scintillation properties in terms of light yield and time decay. It was suggested that such ions, irrespective of their valence, introduce local disorder and cause the formation of point defects acting as traps and affecting the migration of charge carriers to the luminescence centres [1-3]. As a matter of fact, irrespective of sintering agents local disorder is inherently present in optical ceramics due to the existence of grain boundaries. Really, such ceramics are intriguing systems characterized by the simultaneous presence of relatively ordered regions within the grains, which constitute the major part of the material volume, and of defect-rich interface regions between grains. In these boundary regions segregation of rare-earth doping ions was also found to occur [4]. Thermally stimulated luminescence (TSL) experiments have been performed on Lu3Al5O12 (LuAG) ceramics doped with Ce3+ or Pr3+ in order to characterize defects in such materials and to compare the results with the defect properties in single crystals [1-3]. In this contribution, we focus on the information that can be obtained from such measurements specifically concerning the occurrence of local disorder, which causes a broadening of glow curves related to inhomogeneous broadening of defect levels. Due to the high concentration of defects and luminescent centres at grain boundaries, the shape of TSL peaks is expected to be particularly sensitive to the quality of such interfaces so that it can be used as a qualitative probe of local disorder and provide a useful tool during material optimization. Our characterization is completed by Raman scattering data providing complementary structural information.

Vedda, A., Dell'Orto, E., Fasoli, M., Moretti, F., Shen, Y., Liu, S., et al. (2014). Detection and control of local structural disorder indello rare-earth doped Lu3Al5O12 optical ceramics. Intervento presentato a: EURODIM 2014, University of Kent - Canterbury (UK).

Detection and control of local structural disorder indello rare-earth doped Lu3Al5O12 optical ceramics

VEDDA, ANNA GRAZIELLA
Primo
;
DELL'ORTO, ELISA CAMILLA;FASOLI, MAURO;MORETTI, FEDERICO;
2014

Abstract

Optical ceramics are finding a strong technological interest in the field of laser and scintillation materials as an alternative to single crystals. The most favourable structural composition is the cubic one; in fact, due to the isotropy of the optical parameters occurring in this case, it is possible to obtain highly transparent bulk materials made of compacted micro - or nano - metric grains. Presently the mostly studied optical ceramics are rare-earth doped Y- and Lu- Aluminium garnets [1, and references therein]. In several cases sintering agents like Si, Mg, Sc, or La are also used. Indeed, it was found that their introduction causes a transparency improvement, accompanied, however, by a deterioration of the scintillation properties in terms of light yield and time decay. It was suggested that such ions, irrespective of their valence, introduce local disorder and cause the formation of point defects acting as traps and affecting the migration of charge carriers to the luminescence centres [1-3]. As a matter of fact, irrespective of sintering agents local disorder is inherently present in optical ceramics due to the existence of grain boundaries. Really, such ceramics are intriguing systems characterized by the simultaneous presence of relatively ordered regions within the grains, which constitute the major part of the material volume, and of defect-rich interface regions between grains. In these boundary regions segregation of rare-earth doping ions was also found to occur [4]. Thermally stimulated luminescence (TSL) experiments have been performed on Lu3Al5O12 (LuAG) ceramics doped with Ce3+ or Pr3+ in order to characterize defects in such materials and to compare the results with the defect properties in single crystals [1-3]. In this contribution, we focus on the information that can be obtained from such measurements specifically concerning the occurrence of local disorder, which causes a broadening of glow curves related to inhomogeneous broadening of defect levels. Due to the high concentration of defects and luminescent centres at grain boundaries, the shape of TSL peaks is expected to be particularly sensitive to the quality of such interfaces so that it can be used as a qualitative probe of local disorder and provide a useful tool during material optimization. Our characterization is completed by Raman scattering data providing complementary structural information.
Si
abstract + poster
optical ceramics; scintillators; optical spectroscopy
English
EURODIM 2014
Vedda, A., Dell'Orto, E., Fasoli, M., Moretti, F., Shen, Y., Liu, S., et al. (2014). Detection and control of local structural disorder indello rare-earth doped Lu3Al5O12 optical ceramics. Intervento presentato a: EURODIM 2014, University of Kent - Canterbury (UK).
Vedda, A; Dell'Orto, E; Fasoli, M; Moretti, F; Shen, Y; Liu, S; Wu, L; Shi, Y; Feng, X; Pan, Y
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/83925
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