S. Solomon, D. Vijayan
UNIVERSITY OF KERALA,
India
Keywords: ceramic, citrate-nitrate synthesis, photoluminescence, solid oxide fuel cells
Summary:
We report, for the first time, the synthesis and detailed characterization of Terbium Samarium Zirconate (TbSmZr₂O₇), a novel oxide ion conductor and photoluminescent material with significant potential for advanced energy and optoelectronic applications. Synthesized using a citrate-nitrate combustion method, TbSmZr₂O₇ crystallizes in a defect-fluorite structure (Fm3m space group), located at the pyrochlore-defect fluorite phase boundary. Structural characterization was performed through X-ray Diffraction (XRD) and Raman spectroscopy, which confirmed the stable defect-fluorite phase. Nanoscale features of the synthesized powder were revealed through Transmission Electron Microscopy (TEM), showing particle sizes ranging from 3 to 9 nm. Field Emission Scanning Electron Microscopy (FESEM) analysis of sintered pellets demonstrated a highly dense and well-sintered microstructure, with a grain size distribution between 0.1 µm and 2 µm, suitable for ionic transport applications. Optical characterization of TbSmZr₂O₇ highlighted its semiconducting behavior with an optical band gap of 1.66 eV and an indirect allowed transition mechanism, making it a promising candidate for optoelectronic devices. Photoluminescence (PL) studies revealed significant excitation bands at 270 nm and 313 nm, corresponding to strong emission bands at 364 nm and 400 nm. The observed photoluminescence is attributed to the intrinsic defect structure of the material, indicating its potential for luminescent applications such as phosphors and UV-excitable displays. Electrical properties were evaluated through impedance spectroscopy, which established TbSmZr₂O₇ as a pure oxide ion conductor over the temperature range of 400°C to 900°C. A notable conductivity value of 1.9 × 10⁻³ S/cm was achieved at 900°C, making it a strong candidate for solid oxide fuel cells (SOFCs), oxygen sensors, and other high-temperature electrochemical devices. The multifunctional properties of TbSmZr₂O₇, including its robust ionic conductivity, nanoscale structure, and luminescence, open up exciting possibilities for integration into cutting-edge technologies. Its ability to combine efficient oxide ion transport with photoluminescent behavior underscores its potential for dual-function applications, such as energy-efficient lighting, solid oxide electrolytes, and optoelectronics. This work highlights the novelty and versatility of TbSmZr₂O₇, positioning it as a promising material for next-generation energy and photonic devices. Further exploration of its compositional tuning and defect structure could lead to even broader applications across scientific and industrial fields, including sustainable energy solutions and high-performance sensors.