Coupled oxide-nitride interface engineering in TiN-modified CuO nanopowders: Multiscale structural evolution, surface chemistry and dielectric transport pathways

Abstract

TiN-modified CuO nanopowders containing 0, 5, 10, 15, and 30 wt% TiN were prepared by a sol-gel-assisted precipitation route and calcined at 400 degrees C to determine how a conductive nitride second phase modifies the structure, surface chemistry, agglomerate architecture, and broadband dielectric response of CuO. X-ray diffraction (XRD) confirmed retention of monoclinic tenorite throughout the CuO-containing series. From pristine CuO to CTiN%30, the median apparent coherent-domain size decreased from 23.4327 to 15.8882 nm, whereas the median apparent microstrain increased from 3.0914 & times; 10-3 to 4.7911 & times; 10-3. Field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy (FE-SEM/EDX) showed a progression from dilute Ti/N decoration to pronounced TiN-rich local heterogeneity at 30 wt% TiN. X-ray photoelectron spectroscopy (XPS) resolved nitride-related Ti-N/N-Ti contributions together with Ti-O-N/Ti-O surface components, establishing partial surface retention of TiN accompanied by oxidation without converting the surface spectra into an unsupported bulk retained-TiN fraction. At 1 kHz, the real permittivity increased from 7.74181 +/- 0.00895 for CuO to 10.05412 +/- 0.00858 for CTiN%30 (+29.9%), while tans remained 0.06980 +/- 0.00088 and the AC conductivity remained (3.390 +/- 0.046) & times; 10-8 S cm-1. The combined results demonstrate that TiNinduced particle-contact heterogeneity can enhance permittivity without a commensurate low-frequency leakage penalty. Mechanistic interpretation is deliberately restricted to evidence-supported correlations; unique separation of electrode, grain-boundary, and CuO/TiN interfacial polarization requires geometry-controlled impedance and electric-modulus analysis.