Impeding conduction by breaking the charge carrier hopping in charge-ordered perovskite BaBiO3 ([formula omitted]): Experimental and theoretical electronic structural correlations

Abstract

BaBiO3 (BBO), a charge-ordered perovskite with mixed-valent states of Bi (Bi3+ and Bi5+), is known for its charge density wave (CDW) semiconducting and topological insulating properties. BBO has been extensively investigated for its superconducting, electrical, and photocatalytic properties. The present study aims to understand the alterations in the CDW and electronic properties of BaBi0.53+Bi0.55+O3 by valence-selective substitution of Bi3+ and Bi5+ with La3+ and Nb5+, respectively, in the solid solutions BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5). The samples synthesized via high-temperature solid-state reaction method were characterized by powder X-ray diffraction and various spectroscopic techniques (FT-IR, Laser Raman, EPR, XPS, and UPS). Impedance analysis revealed an upsurge in total impedance with the substitution of Bi3+/Bi5+ by La3+/Nb5+ indicating the blocking of electron/hole hopping by disruption of the charge ordering of redox pair Bi3+ and Bi5+. The valence-selective substitution of Bi3+/Bi5+ in BaBiO3 resulted in an alteration of the electronic structure and changes in the bandwidth of BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5) solid solutions, which were confirmed by both theoretical density of states (DOS) calculations and experimental ultraviolet photoelectron spectroscopic (UPS) studies.