¹ School of Science, Jinling Institute of Technology, Nanjing 210093, China;

² Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices, Huizhou University, Huizhou 516001, China

* Correspondence: wrx@jit.edu.cn

The upconversion photoluminescence properties of CaBi₄Ti₄O₁₅ ceramics co-doped with Yb³⁺, Ho³⁺ ions were investigated, aiming at their potential application in temperature sensing. X-ray diffraction confirmed the successful synthesis and pronounced textured characteristics of the ceramics. Under 980 nm laser excitation, the CaBi_3.96-xYb_0.04Ho_xTi₄O₁₅ (x = 0.01, 0.02, 0.03, 0.04) textured ceramics exhibited three distinct emission bands at 549 nm, 660 nm and 759 nm, corresponding to the transitions ⁵F₄→⁵I₈, ⁵F₅→⁵I₈ and ⁵F₅→⁵I₆ of Ho³⁺ ions. Emission intensities increased with Ho³⁺ concentration, suggesting the absence of concentration quenching. Power-dependent studies confirmed two-photon processes as the origin of three emission bands. Temperature-dependent measurements revealed monotonic thermal quenching, with CaBi_3.93Yb_0.04Ho_0.03Ti₄O₁₅ showing the strongest decrease in fluorescence intensity. Luminescence analysis showed near-infrared emission at 759 nm delivered the highest sensitivity, achieving maximum absolute sensitivity of 0.0072 K^-1 and relative sensitivity of 1.71% K^-1. These results demonstrate that Yb³⁺, Ho³⁺ co-doped CaBi₄Ti₄O₁₅ textured ceramics are promising candidates for luminescence-based temperature sensing applications.