Cu doped ZrO₂ nanoparticles: an optically tuned material with superior structural, electrical and dielectric characteristics

A chemical co-precipitation method was used to prepare pure and Cu-doped ZrO₂ nanoparticles at different doping concentrations (1, 3 and 5 molar %). A comprehensive study of structural and spectroscopic examination confirmed the monoclinic phase with some peaks corresponds to tetragonal phase. No other impurity phase was detected after incorporation of Cu in ZrO₂ lattice. FESEM analysis revealed the fine morphology with narrow size distribution with their elemental compositions. Spherical nanoparticles can be clearly seen in pure ZrO₂ sample while 1% Cu-doped sample displayed few needle like structure along with NPs and large number of needles can be seen in 5% Cu-doped sample. UV Vis spectroscopy exposed that Cu–ZrO₂ NPs exhibit improved light absorption ability and modified bandgap due to the combined effect of interstitial sites and quantum confinement. A red shift in the band absorption edge i.e. from 251 to 260 nm was observed and the bandgap was found to be deceasing from 4.8 to 4.55 eV in ZrO₂ samples with Cu content which validate the presence of defects and oxygen vacancies. Dielectric characteristics i.e., dielectric constant (ε') and dielectric loss (tan δ), and ac conductivity were measured at in wide frequency range from 1000 Hz to 15 MHz. Thus, it was exposed that the doping of Cu in ZrO₂ leads to attain a tuned bandgap with high dielectric constant and low loss, which encourages the use for optoelectronic applications.