Probing the Signature of Disordering and Delocalization of Oxygen Vacancies and Anti-site Defects in Doped LaAlO<sub>3</sub> Solid Electrolytes
Minal Gupta, Omkar V. Rambadey, Shraddha Shirbhate, Smita Acharya, Archna Sagdeo, Pankaj R. Sagdeo
Abstract
Correlation of structural, vibrational, and optical properties with the oxygen ion conductivity mechanism in Ca and Mg single and co-doped LaAlO3 solid electrolytes synthesized via the sol–gel technique has been explored in the intermediate temperature range of 350–700 °C. The disordering of oxygen vacancies has been analyzed through temperature-dependent Raman spectroscopy in doped LaAlO3. Faster disordering of oxygen defects associated with AlO6 octahedra and LaO12 dodecahedra has been observed in lesser distorted samples (higher Ca content) with temperature, but at the same time, the defect concentration of oxygen vacancies crucially impacts the ionic conductivity mechanism. Experimental evidence of oxygen and anti-site defects has been probed through optical absorption spectroscopy in the diffused reflectance mode, wherein the temperature-dependent diffuse reflectance spectra indicate the delocalization of oxygen vacancies and anti-site defects above 250 and 300 °C, respectively. Comprehensively, temperature-dependent Raman and optical absorption spectroscopies have emerged as influential techniques for probing the signature of disordering and delocalization of oxygen vacancies and anti-site defects in solid-state oxide-based materials.