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High-efficiency energy transfer (ET) from Sm 3+ to Eu 3+ leads to dominant red emission in Sm 3+ , Eu 3+ co-doped single-phase cubic CeO 2 phosphors. In this work, a series of Sm 3+ singly and Sm 3+ /Eu 3+ co-doped CeO 2 cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm 3+ singly doped CeO 2 phosphor emitted strong yellow-red light at 573 nm ( 4 G 5/2 - 6 H 5/2 ) and 615 nm ( 4 G 5/2 - 6 H 7/2 ). Meanwhile, the CeO 2 :Sm 3+ , Eu 3+ phosphors showed the emission characteristic of both Sm 3+ and Eu 3+ , with the highest emission intensity at 631 nm. The emission intensity of Sm 3+ decreased with increasing Eu 3+ content, suggesting the ET from Sm 3+ to Eu 3+ in the CeO 2 :Sm 3+ , Eu 3+ phosphors. The decay kinetics of the 4 G 5/2 - 6 H 5/2 transition of Sm 3+ in the CeO 2 :Sm 3+ , Eu 3+ phosphors were investigated, confirming the high-efficiency ET from Sm 3+ to Eu 3+ (reached 84%). The critical distance of energy transfer ( R C = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm 3+ to Eu 3+ in CeO 2 :Sm 3+ , Eu 3+ phosphors is an excellent strategy to improve the emission efficiency of Eu 3+ ., Competing Interests: The authors declare that they have no conflict of interest., (This journal is © The Royal Society of Chemistry.)

The weak emission intensity of rare-earth element-doped dual-mode materials leads to low-sensor sensitivity, which is a challenge in optical sensor applications. The present work achieved high-sensor sensitivity and high green color purity based on the intense green dual-mode emission of Er/Yb/Mo-doped CaZrO 3 perovskite phosphors. Their structure, morphology, luminescent properties, and optical temperature sensing properties have been investigated in detail. Phosphor shows a uniform cubic morphology with an average size of approximately 1 μm. Rietveld refinement confirms the formation of single-phase orthorhombic CaZrO 3 . Under the excitation of 975 and 379 nm, the phosphor emits pure green up and down-conversion (UC and DC) emission at 525/546 nm corresponding to 2 H 11/2 / 4 S 3/2 - 4 I 15/2 transitions of Er 3+ ions, respectively. Intense green UC emissions were achieved because of energy transfer (ET) from the high-energy excited state of Yb 3+ -MoO 4 2- dimer to the 4 F 7/2 level of Er 3+ ion. Furthermore, the decay kinetics of all obtained phosphors confirmed ET efficiency from Yb 3+ -MoO 4 2- dimer to Er 3+ ions, leading to strong green DC emission. Moreover, the DC of the obtained phosphor shows that a sensor sensitivity value of 0.697% K -1 at 303 K is higher than the UC (0.667% K -1 at 313 K) because the thermal effect generated by the DC excitation source light is ignored compared with UC luminescence. CaZrO 3 :Er-Yb-Mo phosphor shows intense green dual-mode emission with high green color purity, 96.50% of DC and 98% of UC emissions, and high sensitivity, making it suitable for optoelectronic devices and thermal sensor applications., Competing Interests: The authors declare that they have no conflict of interest., (This journal is © The Royal Society of Chemistry.)