Influence of Ni doping on room temperature electrical and magnetic properties of WO3 synthesized by solid state route

Tungsten trioxide (WO 3 ) is a promising functional material; however, its limited magnetic response and tunable electronic properties restrict its broader application in advanced electronic and sensing devices. To address these limitations, the present study aims to investigate Ni-doped WO 3 as a dilute magnetic semiconductor, focusing on the role of defect states and carrier dynamics in tailoring its multifunctional properties. For this, a series of W 1-x Ni x O 3 (x = 0–0.06) samples were synthesized via a conventional solid-state reaction route. X-ray diffraction analysis confirms the stabilization of the monoclinic WO 3 phase, with a solubility limit of Ni up to x ≤ 0.06. Increasing Ni incorporation leads to a pronounced decrease in both the average crystallite size and grain size. X-ray photoelectron spectroscopy analysis reveals that the concentration of oxygen vacancies ( V o ) systematically increases with increasing Ni dopant concentration. Raman analysis confirmed the retention of the monoclinic WO 3 phase upon Ni incorporation, with no observable peak shift, indicating successful doping without structural distortion. Optical studies indicated a widening of the bandgap with increasing carrier concentration, consistent with the Burstein-Moss shift. Hall measurements indicate n-type conductivity with enhanced carrier concentration and reduced mobility, suggesting defect-mediated charge transport, which supported increase of V o . Dielectric analysis revealed an increase in both dielectric constant and loss, attributed to carrier hopping and the presence of Ni-O-W dipolar complexes. Electrical transport was dominated by frequency-dependent hopping conduction, with impedance analysis confirming reduced resistance at moderate doping. Magnetic measurements demonstrate weak room-temperature ferromagnetism, which is interpreted using the bound magnetic polaron model, where V o act as localized centers facilitating magnetic coupling between Ni ions. Overall, Ni doping effectively modulates defect states, carrier concentration, dielectric response, and magnetic ordering in WO 3 . The strong correlation among V o , charge carrier dynamics, and magnetism highlights W 1-x Ni x O 3 as a promising candidate with significant potential for applications in gas sensing, electronics and spintronic devices.