Host-Sensitized Photoluminescence and Coordination Environment Evolution in Ba6(Bi1- xTb x)9B79O138 (0 ≤ x ≤ 1).

Borates are well-known candidates for optical materials and, here, we are particularly interested in Ba6Bi9B79O138 (BBBO), which has an interesting layered-type structure and Bi3+-containing characteristics that has prompt us to explore its host-sensitized photoluminescence (PL). Solid solutions of BBBO: xTb3+ (0 ≤ x ≤ 1) were prepared and its host-sensitized photoluminescence was confirmed, which is a result of the efficient Bi3+-to-Tb3+ energy transfer. Furthermore, an evolution of the coordination environments of the Bi3+/Tb3+ sites was observed when increasing x. This evolution was found to correlate to the variation of the PL spectra. In particular, the value of the ratio of cyan/green [defined as I(5D4→7F6)/ I(5D4→7F5) of Tb3+] was about 0.28 when x < 0.4, and it increased to 0.71 at x = 0.9 and thereafter remained almost constant. Ba6(RE0.3- yBi yTb0.7)9B79O138 (RE = La or Y, 0 ≤ y ≤ 0.3) were also prepared for better understanding of the host-sensitization effect and in both series, Ba6(RE0.1Bi0.2Tb0.7)9B79O138 show the highest emission. [ABSTRACT FROM AUTHOR]