Enhanced gyromagnetic properties of Cu-substituted LiZnTi ferrites for LTCC applications

In this work, we prepared a type of LiZnTiCu ferrite with a large grain size and enhanced magnetic properties at ～900 °C by substituting Cu²⁺ ions and doping LBSCA glass. Rietveld refinement of XRD patterns indicates that the Fe³⁺ ions in B sites are partially replaced by the Cu²⁺ ions, which causes the monotone increase of lattice constant. SEM results show that the interaction of CuO nanoparticles and LBSCA glass causes two changes in the grain growth of the LiZnTiCu ferrites. The grain growth is suppressed when the amount of CuO nanoparticles is less than a threshold value (x = 0.05 for 900 °C; x = 0.20 for 875 °C). However, when enough CuO nanoparticles are added, the ferrites possess a large and compact microstructure. The variation of magnetic hysteresis (M-H) loops confirms that M_s follows the Néel's collinear spinel model with the increasing number of CuO nanoparticles (x ≤ 0.25). Finally, a type of LiZnTiCu ferrite (x = 0.15) with uniform large grains (average size >10 μm) and good magnetic parameters (4πM_s = 3457.59 G, H_c = 224.4 A/m and B_s = 236.4 mT) is obtained at ～900 °C.