Multi-dimensional tailoring of the thermometric behaviors of Er3+/Yb3+-codoped Y2W3O12 polychromatic upconverting microparticles for multi-mode visual optical thermometry

To combat the thermal quenching and inadequate sensitivities of luminous materials, the Y1.98–2xW3O12:0.02Er3+/2xYb3+ (YWO:Er3+/2xYb3+; 0.01 ≤ x ≤ 0.11) microparticles with splendid negative thermal expansion (NTE) effect were designed. Excited at 980 nm, the produced samples emit polychromatic upconversion (UC) emissions triggered by the energy back transfer from Er3+ to Yb3+ and it has been systematically discussed via steady-state rate theory. The thermally enhanced UC emissions are accomplished in YWO:Er3+/2xYb3+ microparticles due to the distinctive NTE properties. Moreover, according to the temperature-associated UC emissions of Er3+ arising from its thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs), the thermometric properties of synthesized microparticles are investigated. When non-TCLs are adopted, the absolute and relative sensitivities of resultant microparticles are 0.0129% and 1.7875% K−1, respectively. Furthermore, through manipulating doping content and spatial mode, the temperature sensing capacities of YWO:Er3+/2xYb3+ microparticles are multi-dimensionally regulated. In addition, contactless temperature recognition can also be realized through analyzing the thermochromic features of final products and its relative sensitivity is 2.1604% K−1. Ultimately, visual optical temperature detection is obtained in designed microparticles via its temperature-related emitting colour. Our findings may provide an important insight into the design of luminescent materials with high sensitivities for multi-mode visual optical thermometry.