Cyclic MAM synthesis and upconversion photoluminescence properties of CaMoO4:Er3+/Yb3+ particles

Upconversion (UC) photoluminescence of Er3+ doped CaMoO4(CaMoO4:Er3+) and Er3+/Yb3+ co-doped CaMoO4 (CaMoO4:Er3+/Yb3+) particles was successfully achieved by a cyclic microwave-assisted metathetic (MAM) method, followed by heat-treatment. Well-crystallized UC CaMoO4:Er3+/Yb3+ particles formed after heat-treatment at 600 °C for 3 h showed a fine and homogeneous morphology with particle sizes of 1–3 μm. At excitation at 980 nm, CaMoO4:Er3+/Yb3+ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region, and a weak 655-nm emission band in the red region. The UC intensities of CaMoO4:Er3+/Yb3+ particles were much higher than that of the CaMoO4:Er3+ particles. The Raman spectra of CaMoO4:Er3+ and CaMoO4:Er3+/Yb3+ particles indicated the detection of additional strong peaks at higher frequencies (618, 575, 492, 420 and 373 cm−1) and at lower frequencies (290 and 234 cm−1).