Structural, electrical and optical properties of pure KNN and bismuth, antimony co-doped KNN ceramics (KNN – Bi, Sb)

The structural, electrical, and optical properties of bismuth (Bi) and antimony (Sb) co-doped potassium sodium niobate (KNN) ceramics were systematically investigated with a focus on their potential for energy harvesting and optoelectronic applications. X-ray diffraction (XRD) analysis revealed notable structural modifications, including the presence of a secondary phase, indicating successful incorporation of dopants and associated lattice distortions. Scanning electron microscopy (SEM) demonstrated a reduction in grain size and the formation of dense microstructures, while energy-dispersive X-ray spectroscopy (EDS) confirmed the chemical homogeneity and purity of the synthesized ceramics.

Optical characterization using UV–Vis spectroscopy showed a narrowing of the band gap and enhanced transparency in the near-infrared region. Notably, the wavelength of maximum transmittance exhibited a red shift from approximately 400 nm–650 nm. Photoluminescence (PL) measurements revealed prominent blue-green emissions, which were attributed to defect-related electronic transitions, underscoring the influence of structural and electronic defects introduced by co-doping.

Dielectric properties were assessed using impedance spectroscopy, revealing an enhancement in the dielectric constant and overall energy conversion efficiency. The findings suggest that Bi and Sb co-doping effectively tailors the multifunctional properties of KNN ceramics, thereby enhancing their suitability for next-generation energy harvesting and optoelectronic devices.