Influence of the addition of CeO2 on the microstructure and the magnetic properties of yttrium iron garnet ceramic

CeO2 was added into yttrium iron garnet materials (YIG). Samples, with a nominal composition of Y3-xCexFe5O12 (Ce:YIG), with x = 0 - 0.6, were prepared by a solid-state sintering method. Based on the experimental results, it can be seen that Ce:YIG ceramic with the necessary densification could be fabricated using a lower sintering temperature than that required for pure YIG ceramic. Furthermore, the solubility limit of Ce3+ ions in this Ce-substituted YIG ceramic, in an ordinary atmosphere, was approximately x = 0.2. When the Ce3+ doping content exceeded the solution limit for Ce:YIG ceramic, a foreign CeO2 phase was residual in the ceramic, which led to impurity of the materials. An excessive addition of CeO2 (x = 0.3. 0.4, 0.6) degrades the remanent magnetization (B,.) and the saturation magnetization, opposite to what occurrs with a small addition of CeO2 (x = 0.1, 0.2). This because the magnetic moment of Ce3+, when substituted for non-magnetic moment of Y3+, leads to a slightly enhanced B-r and saturation magnetization; nonmagnetic inclusion of CeO2 inside the material however could degrade these characteristics. Nevertheless, the coercivity (H-c) of the Ce-content samples, using the optimized sintering temperature, increased as the addition increased, due to the decrease in grain size. Consequently, a smaller addition of CeO2 into the YIG material not only lowers the sintering temperature, to achieve a higher density ceramic, but also slightly enhances B-r and the saturation magnetization. (c) 2005 Elsevier B.V. All rights reserved.