Thermal-dependent luminescence in Er³⁺-doped BaHfO₃ and SrHfO₃ perovskites: Improve temperature sensing via Ba-Sr exchange

• Published in: Ceramics international 2024-09
• Main Authors: López-Esquivel, Raul Isaac, Becerril, Luis, Salas-Juárez, Christian Javier, Guzmán-Mendoza, Jose, Falcony, Ciro
• Format: Article
• Language: English
• Subjects: Optical properties in lanthanides; Perovskite structure; Thermal properties
• ISSN: 0272-8842
• DOI: 10.1016/j.ceramint.2024.08.475

The luminescence process behavior stimulated by temperature changes is examined by using the theory of thermally coupled energy levels of erbium ion (Er3+) 2H11/2 and 4S3/2. The different mechanisms and environments are compared and elucidated in crystalline structures of BaHfO3 and SrHfO3 as a product of the atomic exchange of Ba2+ for Sr2+ respectively. The undoped and erbium-doped materials were synthesized by hydrothermal route, the erbium-doped materials were impurified with different Er3+ concentrations; 0.25, 0.5, 1, 3, and 5 at.%. X-ray diffraction (XRD) patterns of both materials present a cubic perovskite-type phase, with space group Pm-3m. High-resolution transmission electron microscopy (HRTEM) micrographs show for both materials the presence of nanocrystals with straight profiles and with an approximate size of 36 nm for BaHfO3 and 32 nm for SrHfO3. The room temperature photoluminescent emission spectra shows the highest luminescent intensity at 1 % Er3+ for both materials, showing different spectral characteristic shapes for each material, due to the different electrostatic forces produced by either Ba2+ or Sr2+ ions surrounding Er3+. Using the “Fluoresce Intensity Ratio” (FIR) technique, the temperature sensing properties of these materials were analyzed and compared from 290 to 330 K covering the well-known physiological range (298.15 K–318.15 K). Both materials, BaHfO3:1%Er3+ and SrHfO3:1%Er3+, show dependence to temperature changes, and the experimental energy gap (ΔE) was used to improve (or decrease) the temperature sensing properties. The theoretical ΔE, maximum relative sensitivity (SRMAX), and the resolution in temperature (δT) were obtained, for BaHfO3: 1 % Er3+ these values were: ΔE = 505.73 cm−1, SRMAX = 0.87 % K−1 at 288.5 K and δT = 0.02 K, while for SrHfO3: 1 % Er3+ the values were: ΔE = 649.21 cm−1, SRMAX = 1.12 % K−1 at 288.5 K and δT = 0.01 K.