Tailoring the properties of alumina ceramic nanoparticles via chromium doping

Abstract

Cr-doped Al₂O₃ (Al₂O₃:Cr) ceramic nanoparticles (AlCr0–AlCr5) are successfully synthesized via the sol–gel method and calcined at 1000 °C. X-ray diffraction (XRD) analysis confirmed the formation of a single-phase α-Al₂O₃ (corundum structure, space group R-3c) with characteristic reflections at 2θ ≈ 25.6°, 35.1°, 37.8°, 43.4°, 52.6°, and 57.5°. The crystallite size increased from ~25 nm for AlCr0 to ~36 nm for AlCr5, accompanied by a reduction in FWHM, indicating improved crystallinity with increasing Cr content. FTIR spectra exhibited characteristic Al–O vibrational bands in the 500–800 cm⁻¹ region, while Raman analysis confirmed Eg and A1g modes of α-Al₂O₃ with enhanced peak intensity at higher doping levels. Density measurements showed an increase in bulk density from ~3.20 to ~3.35 g/cm³ and a corresponding decrease in apparent porosity from ~28% to ~22% with increasing Cr concentration. Thermal analysis revealed total weight loss decreasing from ~6.0% (AlCr0) to ~4.3% (AlCr5), indicating enhanced thermal stability. DSC results showed an exothermic crystallization peak around ~800–830 °C, becoming sharper with Cr addition, while DTG confirmed reduced decomposition rates at higher doping levels. ICP-OES analysis demonstrated composition-dependent Cr³⁺ ion release, decreasing from ~0.007 ppm (AlCr0) to ~0.002 ppm (AlCr5), reflecting improved chemical stability. Cr incorporation enhances crystallinity, densification, thermal stability, and chemical resistance without altering the α-Al₂O₃ phase. Among all samples, AlCr5 exhibited the best overall performance, making it a promising candidate for advanced ceramic applications.