Structural, optical, and electrical characterization of TiO2-doped yttria-stabilized zirconia electrolytes grown by atomic layer deposition

Abstract

Electrolyte material optimization is crucial for electrochemical energy storage devices. The specific composition and structure have an impact on conductivity and stability, both of which are essential for efficient device performance. The effects of controlled incorporation of TiO2 into a Yttria-Stabilized Zirconia (YSZ) electrolyte using the atomic layer deposition (ALD) technique are investigated in this study. The surface chemical composition analysis reveals variations in the Ti oxidation state and a decrease in the O/(Zr + Y + Ti) ratio as TiO2 concentration increases. The formation of acceptor states near the valence band is proposed to reduce the bandgap with the Fermi level. The structural properties indicate that as TiO2 concentration increases, surface homogeneity and crystallite size increase. The contact angle with water indicates a hydrophobic behavior influenced by surface morphology and potential oxygen vacancies. Finally, electrical properties, measured in Ru/TiO2-doped YSZ/Au capacitors operated at temperatures between 100 and 170 °C, showed that the TiO2 incorporation improved the ionic conductivity, decreased the activation energy for conductivity, and improved the capacitance of the cells. This study highlights the importance of the ALD technique in solid-state electrolyte engineering for specific applications, such as energy storage devices.