A new molybdate host material: Synthesis, upconversion, temperature quenching and sensing properties

A new upconversion (UC) host material YbMoO 4 with 0–100   mol% Er 3+ doping was obtained using a facile coprecipitation method. A pure tetragonal phase of YbMoO 4 was synthesized, which was dependent on the pH value of the reaction mixture and the sintering temperature . The existence of pentavalent molybdenum was confirmed in YbMoO 4 by thermal-reduction of hexavalent molybdenum. Under a 976   nm laser diode excitation, both green and red UC emissions were observed from Er 3+ :YbMoO 4 , which corresponded to the 2 H 11/2 / 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ with the strongest luminescence appearing at a mole ratio of Er:Yb=1:10. The two-photon absorption UC process was responsible for the green and red emissions. The temperature-dependent green UC emission of Er 3+ :YbMoO 4 was observed, which was rationalized using the thermal quenching model. The fluorescence intensity ratio (FIR) of green UC emissions was studied as a function of temperature and its high thermal sensitivity implied that the Er 3+ :YbMoO 4 material is a promising prototype for applications in optical temperature sensing.