Temperature Sensing Using Thermal Population of Low-Lying Energy Levels with (Sm0.01Gd0.99)VO4

A temperature sensing scheme is proposed that is based on the dramatic temperature dependence of the photoluminescence when Sm3+ dopants are excited from thermally populated 6H7/2,9/2 levels, rather than the ground level 6H5/2, to the 4G5/2 luminescent level. The scheme has the advantage of eliminating laser heating and background Stokes-type scattering noise. Experimental realization was carried out on a (Sm0.01Gd0.99)VO4 sample by detecting the intensities at 550–580 nm using excitation wavelengths of 601.6 nm (process A) and 644.0 nm (process B) to excite Sm3+ to the 4G5/2 level from the 6H7/2 and 6H9/2 levels, which are ca. 1160 and ca. 2270 cm–1 above the ground 6H5/2 level, respectively. The sensitivities achieved are 1267 K/T2 in the temperature range of 183–413 K for process A and 2600 K/T2 in 393–603 K for process B. At even higher temperatures (600–800 K), a complementary process C based on the temperature-dependent luminescence decay lifetime resulted in a relative temperature sensitivity incre...