Photoluminescent Layered Lanthanide Silicates

• Published in: Journal of the American Chemical Society 2004-08, Vol.126 (33), p.10410-10417
• Main Authors: Ananias, Duarte, Kostova, Mariya, Almeida Paz, Filipe A, Ferreira, Artur, Carlos, Luís D, Klinowski, Jacek, Rocha, João
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other solid inorganic materials; Photoluminescence; Physics
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja047905n

The hydrothermal synthesis and structural characterization of layered lanthanide silicates, K3[M1 - a Ln a Si3O8(OH)2] (M = Y3+, Tb3+; Ln = Eu3+, Er3+, Tb3+, and Gd3+), named AV-22 materials, are reported. The structure of these solids was elucidated by single-crystal (180 K) and powder X-ray diffraction and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, 29Si MAS NMR, and photoluminescence spectroscopy. The Er-AV-22 material is a room-temperature infrared phosphor, while Tb- and Eu-AV-22 are visible emitters with output efficiencies comparable to standards used in commercial lamps. The structure of these materials allows the inclusion of a second (or even a third) type of Ln3+ ion in the framework and, therefore, the fine-tuning of their photoluminescent properties. For the mixed Tb3+/Eu3+ materials, evidence has been found of the inclusion of Eu3+ ions in the interlayer space by replacing K+ ions, further allowing the activation of Tb3+-to-Eu3+ energy transfer mechanisms. The occurrence probability of such mechanisms ranges from 0.62 (a = 0.05) to 1.20 ms-1 (a = 0.1) with a high energy transfer efficiency (0.73 and 0.84, respectively).