Photoluminescence and thermostimulated luminescence processes in rare-earth-doped CaSO4 phosphors

Lakshmanan, A.

doi:10.1016/s0079-6425(99)00003-1

Cited by 103 publications

(48 citation statements)

References 98 publications

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“…Several studies of CaSO 4 phosphors doped with europium have been reported over the last 25 years, showing that the CaSO 4 : Eu system is very complicated [2]. The presence of both divalent and trivalent forms of Eu depends on many factors: synthesis method, thermal preannealing, ionizing irradiation, .…”

Section: Discussionmentioning

confidence: 99%

“…It should allow a better understanding of the TSL mechanisms in CaSO 4 : RE [2,3], usually explained by two models: the``redox reactionº model [4] and the``recombination/energy transferº model [4±6]. The structure of CaSO 4 has an orthorhombic symmetry (D 2h space group); the unit cell contains four molecules with SO 4 tetrahedra and CaO 8 irregular triangular dodecahedron groups.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Thermal Preannealing on Fluorescence, Thermostimulated Luminescence and Cathodoluminescence of CaSO4 Doped with Europium

Lapraz

Prévost

Baumer

et al. 2000

phys. stat. sol. (a)

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This study addresses the important influence of air thermal preannealings (500±1150 C) on the emissions of Eu 2+ and Eu 3+ ions in CaSO 4 samples doped with various Eu concentrations (10±2000 ppm) and synthesized under oxidizing conditions. The characteristics of optical excitation, optical absorption, fluorescence and cathodoluminescence spectra are given before and after the annealings. The role of UV, X-ray or electron irradiation is discussed. An irreversible conversion Eu 3+ 3 Eu 2+ is obtained beyond 600±900 C, even for low Eu concentrations (<50 ppm). There exists an intense change in the ratio of Eu 2+ /Eu 3+ emissions at about 25±100 ppm. Moreover, the present paper shows again how careful one must be with the interpretation of the presence of Eu 2+ in CaSO 4 : Eu when considering cathodoluminescence results only. Two types of Eu 2+ centres seem to be obtained in CaSO 4 : Eu 3+ by thermal preannealings and/or under ionizing (X-ray, cathode-ray) irradiations.Cette e Â tude re Â ve Á le l'importance des recuits thermiques (500±1150 C) sous air du CaSO 4 : Eu sur les e Â missions des ions Eu 2+ et Eu 3+ , pour des e Â chantillons synthe Â tise Â s dans des conditions oxydantes et pour diffe Â rents dopages compris entre 10 et 2000 ppm. Les spectres d'excitation optique, d'absorption optique, de fluorescence et de cathodoluminescence sont donne Â s avant et apre Á s recuit. Le ro Ã le des excitations UV, X ou e Â lectronique est souligne Â. On confirme une conversion irre Â versible Eu 3+ 3 Eu 2+ en fonction de la tempe Â rature du recuit (sous air), principalement dans l'intervalle 600±900 C, et cela me Ã me pour de tre Á s faibles dopages (< 50 ppm). Il existe une forte variation du rapport des e Â missions Eu 2+ /Eu 3+ autour de 25±100 ppm. De plus ce travail indique de nouveau qu'il faut e Ã tre prudent dans l'interpre Â tation de la pre Â sence d'ions Eu 2+ dans CaSO 4 : Eu au vu des seuls spectres de cathodoluminescence. Deux types de centres Eu 2+ semblent se former dans CaSO 4 : Eu 3+ apre Á s pre Â recuit thermique et/ou irradiation ionisante (X, rayonnement cathodique).

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Thermal Preannealing on Fluorescence, Thermostimulated Luminescence and Cathodoluminescence of CaSO4 Doped with Europium

Lapraz

Prévost

Baumer

et al. 2000

phys. stat. sol. (a)

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“…Trivalent Dy could be incorporated into CaSO 4 lattice only by recrystallization in H 2 SO 4 medium. Monovalent co-dopants such as Na + or Li + could, however, be incorporated into CaSO4:Dy lattice by cold pressing followed by sintering [8].…”

Section: Pelletization and Sinteringmentioning

confidence: 99%

The Role of Sintering in the Synthesis of Luminescence Phosphors

Lakshmanan¹

2012

Sintering of Ceramics - New Emerging Techniques

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“…The different colors of luminescence from gypsum under ultraviolet (UV) light excitation have been reported as baby blue, creamy green, greenish white, yellow green, and yellow. Some investigators synthesized gypsum crystals (Kastner, 1970;Cody, 1976;Cody and Cody, 1988;van der Voort and Blasse, 1989;de Meer et al, 2000), and many investigators studied the luminescence properties of alkaline -earth sulfates activated with rare -earth (RE) ions (Nambi and Bapat, 1980;Yamashita et al, 1985;van der Voort and Blasse, 1990;Lakshmanan, 1999;Yamashita et al, 2001). However, the origin of luminescence from natural gypsum has not been identified (Robbins, 1994).…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence properties of gypsum

Masaru¹,

Kono²,

Yamashita

2011

Journal of Mineralogical and Petrological Sciences

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The photoluminescence (PL) properties of four gypsums from three localities, namely, Inner Mongolia (China), Turkey, and Canada, are investigated at room temperature. Under 365 -nm excitation, two types of gypsums from Inner Mongolia exhibit different luminescence colors, namely, yellow and cyan -white, and gypsums from Turkey and Canada exhibit yellow and bluish -white luminescence, respectively. The PL spectra of these gypsums consist of continuous sub -bands distributed in all visible wavelengths, and the excitation spectra of these gypsums consist of continuous sub -bands distributed in a wide range of wavelengths, i.e., 200 -500 nm. The features of PL and excitation spectra suggest that the origin of luminescence from these gypsums may be luminescent organic substances included into crystals in the growth process rather than the impurity ions substituted for Ca 2+ .

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Photoluminescence and thermostimulated luminescence processes in rare-earth-doped CaSO4 phosphors

Cited by 103 publications

References 98 publications

Effect of Thermal Preannealing on Fluorescence, Thermostimulated Luminescence and Cathodoluminescence of CaSO4 Doped with Europium

Effect of Thermal Preannealing on Fluorescence, Thermostimulated Luminescence and Cathodoluminescence of CaSO4 Doped with Europium

The Role of Sintering in the Synthesis of Luminescence Phosphors

Photoluminescence properties of gypsum

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