Synthesis of spray deposited transition metals doped (Cr, Mn, Fe, Ni, and Cu) compositionally complex ZnO thin films with enhanced band gap and magnetism

Compositionally complex ceramics (CCCs) is now considered as a subgroup of high entropy ceramics (HECs); which focuses on the further opportunities of exploring wide compositional spaces and low entropy options of HECs. This study for the first time attempts to render high configurational disorder in the cationic site of ZnO lattice through the incorporation of higher concentration quinary 3d transition metals dopants i.e. Cr, Mn, Fe, Ni, and Cu. The authors here demonstrate the synthesis of pure ZnO and compositionally complex (Ba_xSr_xMn_xFe_xNi_x) Zn_1-5xO (where x = 0.02, 0.04, and 0.06; the samples denoted as 10CCZO, 20CCZO, and 30CCZO respectively) thin films by low-cost spray pyrolysis technique at 250 °C. In order to investigate the unique wurtzite phase stability of all CCZO crystal structures, XRD analyses were carried out with Rietveld refinement. XRD study showed the single hexagonal wurtzite phase presence of P63mc space group in all CCZO samples and notable change in lattice parameters with doping increment. SEM results revealed a significant change in surface morphology as it transformed flake-shaped grains for pure ZnO to flower and interconnected flake patterns. UV–visible spectroscopy disclosed enhanced transmittance and optical band gap of 3.94, 3.97 eV in 10CCZO and 20CCZO, respectively. VSM test showed that the magnetization values increased substantially in CCZO thin films indicating the potential prospect of these CCZO in magneto-optical applications. In addition, tuned functional properties were correlated with microstructural features.