• Cu-doped ZnO (Zn 1-x Cu x O) nano-ceramics were prepared by ball-milling of the CuO and ZnO powders. • Up to 3 at% of Cu could be doped in ZnO via ball milling, beyond which Cu precipitates as CuO during calcination. • The ac... more
• Cu-doped ZnO (Zn 1-x Cu x O) nano-ceramics were prepared by ball-milling of the CuO and ZnO powders. • Up to 3 at% of Cu could be doped in ZnO via ball milling, beyond which Cu precipitates as CuO during calcination. • The ac conductivity values decrease by Cu doping in ZnO, making it a better dielectric material. • Cu doping in ZnO via ball milling is cost effective and scalable to industrial level. Nanocrystalline Cu doped ZnO (Zn 1-x Cu x O, x = 0, 0.01, 0.02, 0.03 and 0.04) samples were synthesized by high energy ball milling technique (HEBM). The strain developed during ball milling and incorporation of Cu into the Zn-site in ZnO lattice is depicted as broadening of the full width at half maximum (FWHM) of the XRD. The X-ray diffraction peak-widths (FWHM) increases with increase in Cu-concentration. Furthermore, the mechanical impact and the heat produced during ball milling helps in the formation of aggregates. The size of these aggregates was observed to increase with Cu-concentration. Upon calcination, these aggregated structures form particle, resulting in bigger particles for higher concentration of Cu. The XRD results confirm that up to ∼3 at% of Cu can be doped in ZnO lattice, beyond which CuO precipitates. The impedance spectroscopy and the ac-conductivity results confirm the improvement in dielectric properties of ZnO by Cu doping. The decrease in magnitude of Z′ on increase in temperature confirms the negative temperature coefficient of resistance (NTCR) behaviour of the samples. The ac conductivity of ZnO decreases with Cu doping and follows the correlated barrier hopping (CBH) model in the investigated temperature and frequency range.
