Hole and Electron Doping Outcomes in Bi₂YO₄Cl

Recognizing the deficiency in the hole and electron doping outcomes in layered bismuth-based oxyhalides intergrowths, the current study was addressed to the doping of Ca²⁺ and Zr⁴⁺ for Y³⁺ in Bi₂YO₄Cl. The samples were rapidly synthesized by a sol-gel auto combustion method and characterized extensively. Up to 30 mol % Y could be substituted with Ca in tetragonal symmetry and without the appearance of any additional phase. The unit cell parameters varied nonlinearly with the elongation of the Y-O bond. The Raman spectra supported the local site distortion. The calcium-substituted samples displayed selected area electron diffraction characteristics similar to those of Bi₂YO₄Cl. A blueshift of the absorption edge was noticed with increasing calcium content yielding optical band gap values in the 2.40-2.57 eV range. The creation of 10% Bi⁵⁺ in Bi₂Y_0.70Ca_0.30O₄Cl was established with the help of XPS measurements and redox titrations. The higher reactivity of Bi⁵⁺ in an aqueous solution has been demonstrated for the oxidation of As(III) to As(V). Electron doping through Zr⁴⁺ incorporation was possible up to 30 mol % in Bi₂YO₄Cl. The Y-O bonds are contracted, and the Bi-O bonds are elongated with increasing Zr⁴⁺ content. Zr⁴⁺'s incorporation induced a local distortion. The color of the sample changed from bright yellow to deep yellow with Zr inclusion, resulting in a progressive decrease in optical band gap values. The introduction of electrons caused the reduction of 13.6% of Bi(III) to Bi(0). These results have established the vulnerability of Bi₂O₂ chains to charge carriers in Bi₂YO₄Cl. Density functional theory (DFT) calculations were implemented to understand the electronic and optical properties of the pristine and doped compounds. From the band structure calculations, the chosen compounds were found to be indirect band gap semiconductors. The results of the DFT calculations were in good agreement with the experiment; however, for the doped cases, virtual crystal approximation has been used considering uniform doping at the Y-site.