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

A new upconversion (UC) host material YbMoO4 with 0-100 mol% Er3+ doping was obtained using a facile coprecipitation method. A pure tetragonal phase of YbMoO4 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 YbMoO4 by thermal-reduction of hexavalent molybdenum. Under a 976 nm laser diode excitation, both green and red UC emissions were observed from Er3+:YbMoO4, which corresponded to the 2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ 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 Er3+:YbMoO4 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 Er3+:YbMoO4 material is a promising prototype for applications in optical temperature sensing.