Ambient‐Pressure Stabilization of β‐GdB3O6 by Doping with Bi3+ and Color‐Tunable Emissions by Co‐Doping with Tb3+ and Eu3+: The First Photoluminescence Study of a High‐Pressure Polymorph. Issue 12 (16th May 2017) - Sun, Xiaorui
Abstract: Rare‐earth borates are good candidates for optical applications. To date, however, the high‐pressure/high‐temperature technique has produced a large number of novel borates with optical properties that have rarely been investigated due to the severe problem of substantial defects. We targeted the high‐pressure polymorph of β‐GdB3 O6 and synthesized three solid solutions of β‐Gd0.75− x Bi0.25 Tb x B3 O6 (0≤ x ≤0.75), β‐Gd0.75− y Bi0.25 Eu y B3 O6 (0≤ y ≤0.75), and β‐Gd0.50− z Bi0.25 Tb0.25 Eu z B3 O6 (0≤ z ≤0.05) by using typical solid‐state reactions at 820 °C. Here, the function of Bi 3+ is to stabilize the high‐pressure phase by lowering the synthetic temperature and being the sensitizer to promote the green and red emissions of Tb 3+ and Eu 3+ . The multiple energy transfer paths were investigated by using lifetime decay experiments and photoluminescent spectra, and both efficiency and mechanism were determined. Eventually, color‐tunable and white emissions were achieved by rational doping of Bi 3+, Tb 3+, and Eu 3+ into β‐GdB3 O6, that is, the CIE chromaticity coordinate for β‐Gd0.44 Bi0.25 Tb0.30 Eu0.01 B3 O6 is (0.318, 0.365) with a correlated color temperature of 6101 K. Abstract : Easing the pressure : The optical properties of the high‐pressure polymorphs of borates have rarely been studied due to the disadvantage of the high‐pressure‐assisted synthetic method. Here, Bi 3+ doping helps the stabilization of the high‐pressure phase of GdB3 O6 at ambient pressure, which thus allowed the systematic investigation of its photoluminescence properties (see figure).