EPR detection of sphalerite ZnO in mechanically treated ZnO+0.1C nanosystem

The EPR spectrum of Mn²⁺ ions observed in nano-powders of wurtzite ZnO phase (ZnO_Wt) with 0.1 wt% of carbon nanoparticles subjected to mechanical processing (MP) for t_MP>90 min where different than the well-known EPR spectrum of Mn²⁺ in ZnO_Wt. Such spectrum was observed earlier and it was attributed to either a new phase or a highly disordered nanocrystalline ZnO_Wt. Spin-Hamiltonian (S-H) parameters and line width (ΔB) have been determined by computer simulation of observed EPR spectrum of Mn²⁺: g=2.0010±0.0004, |A|=(73.6 ±0.3)·10^-4 cm^-1, |D|=(102 ±30)·10^-4 cm^-1, ΔB≈0.6 mT. The comparison of S-H parameters of the EPR spectra of Mn²⁺ ions in a new formed phase and in ZnO_Wt indicates that the parameter A of the hyperfine structure in a new phase is slightly smaller and that the D parameter is more than two times lower than in ZnO_Wt. The content of the newly formed phase (~1% to 2%) is significantly higher than the content of external impurity states in the initial ZnO sample. The observed EPR spectrum is attributed to the Mn²⁺ ions in the zinc blende (sphalerite) ZnO phase (ZnO_ZB), created on the surface of ZnO_wt nanoparticles during mechanical processing.