Through the DC arc discharge plasma method, ZnO:Er³⁺/Yb³⁺ hierarchical nanorod optical temperature-sensing materials were successfully prepared using ZnO powder, Er₂O₃ powder, and Yb₂O₃ powder as raw materials in an oxygen (O₂) atmosphere. The crystal structure, morphological characteristics, and upconversion luminescence properties of the samples were systematically characterized through XRD, Raman, XPS, SEM, TEM, and photoluminescence analyses. Both XRD and Raman analyses indicated the absence of secondary phases in the samples, and the XRD and Raman spectra of ZnO:Er³⁺/Yb³⁺ exhibited a low-angle shift compared to undoped ZnO, confirming the substitution of Er or Yb ions at the main Zn lattice sites. XPS confirmed the coexistence of Zn, O, Er, and Yb elements, while EDS quantitative analysis revealed an atomic ratio of Zn:O:Er:Yb as 47.22:46.47:0.81:4.33. SEM results showed that the hierarchical nanorod structure consists of a robust main trunk and numerous radial branches grown from the main surface. Each nanorod maintained a uniform diameter along its entire length, with an average diameter ranging from 20 nm to 45 nm and a length of approximately 500 nm. HRTEM revealed that the adjacent lattice fringe spacing of the branched nanorods was about 0. 271 nm, corresponding to the (002) plane spacing of wurtzite-type ZnO, confirming their well-crystallized single-crystal structure. This result also indicated that the [001] crystal orientation is the primary growth direction of the ZnO nanorods. Photoluminescence studies identified characteristic emission peaks at 525 nm, 546 nm, and 662 nm in the visible region, attributed to the intra-4f electronic transitions of Er³⁺ ions. Through temperature-dependent luminescence tests from 298 K to 573 K, the maximum relative sensitivities of the fluorescence intensity ratios for the thermally coupled levels (²H_11/2 and ⁴S_3/2) and non-thermally coupled levels (⁴S_3/2 and ⁴F_9/2) were determined to be 1.03 % K^-1 and 2.20 % K^-1, respectively, while the maximum relative sensitivity of the ⁴S_3/2 level fluorescence lifetime was 2.43 % K^-1. In this study, a single luminescent center is used to achieve three-mode optical temperature measurement. The ZnO:Er³⁺/Yb³⁺ hierarchical nanorod optical temperature-sensing material demonstrated excellent signal discrimination and high sensitivity across a broad temperature range, highlighting its significant potential for applications in optical temperature sensing.

Key words: Zinc oxide, Rare earth doping, Optical temperature measurement, Upconversion luminescence, Fluorescence lifetime