Hongwei Yang,Fang Xu,Yulong Liao,Yong Ren,Guixiang Liu,Yan Yang,Xueying Wang,Bo Dai
In this work, we prepared a type of LiZnTiCu ferrite with a large grain size and enhanced magnetic properties at ∼900 °C by substituting Cu 2+ ions and doping LBSCA glass. Rietveld refinement of XRD patterns indicates that the Fe 3+ ions in B sites are partially replaced by the Cu 2+ 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 (4π M s = 3457.59 G, H c = 224.4 A/m and B s = 236.4 mT) is obtained at ∼900 °C.
A series of Zn 2- x Cu x GeO 4 ceramics were prepared by the solid-phase sintering method. Cu 2+ substitution for Zn 2+ facilitated the single-phase formation and benefited densification via lowering the sintering temperatures , hence thereby the microwave dielectric properties were largely improved. A representative composition with x = 0.08 revealed a homogenous Zn 2 GeO 4 phase with good microwave dielectric properties: ε r ∼ 7.47, Q × f ∼ 56,980 GHz, and τ f ∼ −13.9 ppm/°C when sintered at 1000 °C. To evaluate the potential application of low-temperature cofired ceramics (LTCC), sintering aids (B 2 O 3 ) were added to the x = 0.08 sample to reduce its sintering temperature to below 960 °C. A dramatic improvement in Q × f ∼ 107,415 GHz was observed with only 0.5 wt % B 2 O 3 addition. Chemical compatibility was confirmed via cofiring with silver electrodes at 940 °C. All the merits show promising potential for advanced substrates.
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