Bandgap Engineering and Excitation Energy Alteration to Manage Luminescence Thermometer Performance. The Case of Sr2(Ge,Si)O4:Pr3+

Having proven that the temperature range of luminescent thermometers can be greatly widened by combining the intra- and interconfigurational transitions of the Pr3+, the possibility to manage important thermometric parameters by bandgap engineering and variation of energy of excitation photons are examined. Partial replacement of Ge with Si to form Sr-2(Ge,Si)O-4:Pr is very useful to manage these luminescence thermometer properties. This allows control of the range of temperatures within which the 5d(1)-> 4f Pr3+ luminescence can be detected. Also, excitation energy appears to affect the thermometer's performance. These allow adjustment of the range of temperatures that can be measured with the highest accuracy, reaching the spectacular value of S-r = 9.2% K-1 at 65 K for a Sr-2(Ge-0.75,Si-0.25)O-4:0.05%Pr3+ thermometer upon 244 nm excitation. For the first time, it has been proven that excitation energy may significantly affect the performance of luminescence thermometers. In Sr-2(Ge-0.75,Si-0.25)O-4:0.05%Pr3+ the highest relative sensitivity shifts from 65 K upon 244 nm excitation (S-r = 9.2% K-1) to 191 K upon 253 nm excitation (S-r = 3.97% K-1). This occurs despite both excitation wavelengths fitting within the 4f -> 5d(1) excitation band. This paper shows that bandgap management is useful to effectively design new luminescent thermometers.