The effect of rare-earth oxide CeO2 on the electromagnetic properties of ferrite-ceramic composite materials
In this work, we present the influence of rare-earth element additions on this new composite material. A great improvement of the electromagnetic properties was obtained. The constituent chemicals were mixed in the stoichiometric composition, calcined at 850degC for 2 h and blended with PVA to press into steroidal or disc shaped specimens. These specimens were sintered at 900degC for 2.5 h in air. The complex permeability, capacity and impedance were measured with HP4291B and 4291A instruments, respectively, in the frequency range from 1MHz to 2GHz.
Electromagnetic properties of a new ferrite-ceramic low-temperature cocalcined (LTCC) composite materials
A new ferrite-ceramic composite material with inductive, capacitive, and impedance properties was fabricated by a solid-state reaction. The composite materials were prepared with ferromagnetic NiCuZn ferrites and ferroelectric BaTiO/sub 3/ perovskite. Co/sup 2+/, Bi/sup 3+/, Y/sup 3+/, Dy/sup 3+/, and Ca/sup 2+/ ions are selected to improve the electromagnetic properties. We found that this new material has excellent frequency dependence of magnetic and dielectric properties, which can be used not only as inductor and resistor materials but also as capacitor materials in the wide range of 1 KHz to 4 GHz. At 1 MHz, the dielectric constant /spl epsiv/' of the composite material is 60-120, and the initial permeability /spl mu/' is 5.6-13.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.