Novel Optical Thermometry Strategy Based on Gd3+ and Defect-Related Luminescence of ZrO2:Gd3+ Nanoparticles

To achieve high-temperature-sensing sensitivity, a new strategy of optical thermometry is designed based on the synergetic luminescence of the radiative emission of lanthanide (Ln) ions and defect-related luminescence in ZrO2:Gd3+ nanoparticles. By X-ray diffraction, Raman spectroscopy, electron paramagnetic resonance spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, temperature-dependent photoluminescence (PL) spectroscopy, decay time measurements, and thermoluminescence study, we investigate the defect nature, the relationship between Gd3+ ions and defect centers, the PL property, and the thermometric performance. Under UV excitation, the broad emission band (lambda(max) = 400 nm) observed is ascribed to the carbon impurities and oxygen vacancies, while the sharp emission peak (lambda(max) = 315 nm) is from Gd3+ ions. Originating from their diverse thermal responses, the fluorescence intensity ratio of defect-related luminescence to Gd3+ emission displays excellent absolute sensitivity (S(a-ma)x = 6.408 K-1), relative sensitivity (Sr-max = 3.452% K-1), and good signal discrimination (Delta lambda(max) = 85 nm), which are much higher than those reported previously for ratiometric thermal-sensing materials. This work may not only pave a way for boosting the sensing sensitivity of optical thermometers but also provide inspiration for extending the application of defect-related luminescent materials in thermal detection.