Structure and luminescence analyses of simultaneously synthesised (Lu 1-x Gd x ) 2 O 2 S:Tb 3+ and (Lu 1-x Gd x ) 2 O 3 :Tb 3

• Published in: Dalton transactions : an international journal of inorganic chemistry 2017-06, Vol.46 (24), p.7693-7707
• Main Authors: Pasberg, Natalie, den Engelsen, Daniel, Fern, George R, Harris, Paul G, Ireland, Terry G, Silver, Jack
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/C7DT00862G

Herein we describe the synthesis and luminescence of nanosized (Lu Gd ) O S:Tb and (Lu Gd ) O :Tb phosphors with y = 0.1 mol% Tb and y = 2 mol% Tb and x ranging between 0 and 1. The concentration of Gd (x) was varied in steps of 0.1 (molar ratio Gd ). The samples at 0.1 < x < 0.7 contained a mixture of (Lu Gd ) O :Tb and (Lu Gd ) O S:Tb , while the samples at x = 0 contained only Lu O :Tb . At 0.1 < x < 0.7 Lu O S:Tb and Gd O S:Tb did not form a solid solution, but rather crystallised into two slightly different hexagonal structures. This behaviour has been explained in terms of segregation of Lu and Gd between the oxide and oxysulfide phases: the oxide phase is more Lu-rich whereas the second oxysulfide phase is more Gd-rich. The photoluminescence spectra of the phosphors with 0.1 mol% Tb showed a modest colour change of the fluorescence light from cyan to green when x was increased from 0 to 1, whereas the samples of the series with 2 mol% Tb yielded essentially green light. From this analysis it was concluded that the colour change of (Lu Gd ) O S:0.1%Tb is caused by increasing energy transfer of the D -level of Tb to the charge transfer band of (Lu Gd ) O S:Tb upon increasing x. Since the samples with 100% Lu consisted of pure cubic Lu O :Tb , we had the opportunity to also study the symmetry-related PL of this compound. From this study we concluded that the C -C doublet of the Tb D → F transition behaves in the same way as the corresponding doublet in cubic Y O :Tb .