Enhanced ionic conductivity through B-site Zr doping in NaNbO3 solid electrolytes

Oxide ion conductors hold significance in various applications, such as electrolytes in solid oxide fuel cells. This study focuses on synthesizing and systematically investigating the structural, morphological, and electrical properties of NaNb_1-xZr_xO_3-0.5x (0 $\le$ x $\le$ 0.15) solid electrolyte. X-ray photoelectron spectroscopy (XPS) analysis shows that introducing a small quantity of zirconium into NaNbO₃ induces an environment of unbalanced charge neutrality, creating oxygen vacancies. This phenomenon establishes a pathway for the mobility of oxygen ions. Temperature-dependent ac conductivity, analyzed through impedance data, follows Jonscher's power law, with the 's' parameter indicating a correlated barrier hopping mechanism. Enhanced conductivity is observed with Nb⁵⁺ substitution by Zr⁴⁺. The reduced activation energy value is observed for x = 0.1, which suggests enhanced ion hopping and, hence, enhanced conductivity. NaNb_0.9Zr_0.1O_2.95 exhibits predominantly ionic conduction with a total conductivity of 6.2 × 10⁻⁴ S cm⁻¹ and bulk conductivity of 1.72 × 10⁻³ S cm⁻¹ at 700 °C. This study shows the promising potential of Zr-doped NaNbO₃ as a solid electrolyte for various electrochemical applications.