Dual-functional of non-contact thermometry and field emission displays via efficient Bi3+ → Eu3+ energy transfer in emitting-color tunable GdNbO4 phosphors

Using solid-state reaction technique, we prepared a series of Bi3+/Eu3+-activated GdNbO4 phosphors. Under 308 nm excitation, the energy transfer from Bi3+ to Eu3+ ions, which belonged to the dipole-quadrupole interaction mechanism, allowed the GdNbO4:Bi3+,Eu3+ compounds to display tunable multi-color emissions. The temperature dependent photoluminescence emission and water resistance behaviors of the obtained samples were investigated in detail. Taking full advantage of the diverse thermal quenching performance between Bi3+ and Eu3+ ions along with their distinct characteristic color emission, we designed a highly sensitive non-invasion optical thermometer. The maximum absolute and relative sensor sensitivities of the final compounds were about 0.0367 K-1 and 3.81% K-1, respectively. Moreover, the as-prepared phosphors exhibited excellent cathode-luminescence properties. These above characteristics indicated that Bi3+/Eu3+-activated GdNbO4 phosphors can be used as potential luminescent materials for non-contact temperature measurement and field emission display.