Upconversion luminescence and ratiometric temperature sensing behavior of Er3+/Yb3+-codoped CaY2Ge3O10 germanate

A new series of CaY2–10xYb9xErxGe3O10 trigermanates (space group P21/c, Z = 4) has been synthesized using an EDTA-assisted method. Under 980 nm laser diode excitation, the samples exhibit intense upconversion luminescence corresponding to the characteristic transitions 2H9/2 → 4I15/2 (400–420 nm), 2H11/2,4S3/2 → 4I15/2 (500–600 nm) and 4F9/2 → 4I15/2 (625–725 nm) in Er3+ ions. The CaY1.5Yb0.45Er0.05Ge3O10 phosphor can be used as a good temperature sensor with high absolute and relative sensitivities Sa(max) = 0.0051 K−1 and Sr(max) = 0.0109 K−1.