“…The samples were defined sample A-F in There is no such phenomenon in the SEM photos of the NiZn ferrite prepared by this co-precipitation method [15], but it was found in the copper-substituted NiZn ferrite by the same process and was proved to be Cu-rich phase [16]. It is assumed that there contains Cu + ions in these small particles on the grain boundaries, which is justified by the decrease of the lattice parameters of the samples sintered at 1000 • C, 1100 • C and 1200 • C in Table 1.…”