Enhancement of up-conversion luminescence efficiency and temperature sensing properties in BaWO4: Ho3+/Yb3+ phosphor via Gd3+ incorporation

In this work, tungstate BaWO4 phosphors doped Ho3+-Yb3+-Gd3+ ions are successfully synthesized through solid-state reaction method. Under the excitation of a 980 nm laser, the up-conversion (UC) luminescence properties are investigated simultaneously. The blue (465 nm, 489 nm), green (541 nm) and red (665 nm) emission intensities of BaWO4: Ho3+/Yb3+/Gd3+ samples are dramatically enhanced by 20.59, 9.83, 7.37, and 27.59 times more than those without Gd3+ ions. The possible reason is discussed, which attributes to the energy transfer efficiency enhancement from Yb3+ to Ho3+ due to the lattice expansion induced by Gd3+ ions. The temperature-sensing properties of BaWO4: Ho3+/Yb3+/Gd3+ samples are also discussed based on the fluorescence intensity ratio (FIR) technology. The sensitivity of temperature measurement for BaWO4: Ho3+/Yb3+/Gd3+ sample is higher than that of BaWO4: Ho3+/Yb3+. It proves that the codoped Gd3+ ions can also increase the temperature sensitivity because the higher UC emission efficiency will lead to a high signal-to-noise ratio. The result provides an effective way to design UC luminescence materials with high temperature sensing properties.