Luminescence of Sr ₆ YAl(BO ₃ ) ₆ activated with Tb ³⁺ and Gd ³⁺ 

Abstract

Synthesis and luminescence properties of novel Sr6YAl(BO3)6 borate belonging to STACK (STACK is an acronym derived from the first letters of the surnames of the inventors; Schaffers, Thompson, Alekel, Cox, Keszler) family was reported for the first time. XRD measurement and Rietveld refinement were performed to check the phase purity of the prepared samples. Photoluminescence emission (PL) and excitation (PLE) spectra were measured for Tb3+ and Gd3+ doped Sr6YAl(BO3)6. The observed emission and excitation spectra show characteristic peaks of Tb3+ and Gd3+. The PLE and PL spectra of Gd3+ arise due to f-f transitions, whereas in the case of Tb3+, the excitation band is ascribed to the f-d transition and emission comes from the f-f transitions. Trivalent activators Tb3+ and Gd3+ occupy Yttrium sites. Owing to fixed, well-separated positions (Y-Y distance 7.67 Å), a large concentration of activators could be activated. As much as 10 mol% activators could be accommodated without causing concentration quenching. Luminescence decay measurements were also performed which shows the lifetime of the order of milliseconds, typical of forbidden f-f transitions, for both Gd3+ and Tb3+ ions. Low concentration quenching makes Sr6YAl(BO3)6borate host attractive for various phosphor applications.