Effect of BaCu(B 2 O 5 ) additions on the sintering behaviors and dielectric-magnetic properties of Co 2 Z hexaferrite
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In this study, BaCu(B2 O5 ) (BCB) is utilized as the sintering aids to decrease the sintering temperature of Ba3 (Co 0.4Zn 0.6) 2Fe 24 O41 [(Co 0.4Zn 0.6) 2 Z]. The influence of BCB addition on the microstructures as well as the dielectric and magnetic properties of the (Co0.4Zn 0.6) 2 Z ceramic samples is investigated. It is found that the 5 wt% BCB added (Co 0.4Zn 0.6 ) 2 Z sintered at 925 °C exhibits both a high relative density of about 95% and a homogeneous microstructure with few pores existing. Both the relative permittivity and permeability of the sample keep stable from 10 to 800 MHz. Also, the dielectric and magnetic loss are low and effectively suppressed within a wide frequency range. For the specimen with 5 wt% BCB, the dielectric and magnetic loss tangent are 0.003 and 0.039 at 200 MHz, respectively. In addition, a compatibility test with Ag powders has been carried out. The optimized properties indicate that this kind of low temperature sintered Z-type hexaferrite is a good candidate for the applications of multilayer chip inductors.
I. INTRODUCTION
With the rapid development of information technology, the miniaturization and high frequency tendency of electronic systems become the main steam. Thus, the downsizing of electronic components must keep pace with the miniaturization trend, while the multilayer chip inductors (MLCIs) have achieved great success. In this way, more and more efforts begin to focus on the preparation of low temperature sintered ferrites, which are the fundamental materials for the MLCIs.1,2 As we all know, Ag is always chosen as the inner conductor of MLCIs to ensure high Q value because of its low resistivity.2,3 So it is important to develop ferrites having low sintering temperature below 960 °C and being able to be co-fired with the Ag electrode. In recent years, the spinel NiZn ferrites have been widely used in MLCIs industry. Compared with the spinel ferrites, the planar hexagonal ferrites possess higher Snoek product, which is beneficial to improve the application frequency.1–9 Therefore, the hexagonal ferrites become ideal soft magnetic materials for the MLCIs. Among these ferrites, the well performed magnetic property of Co2Z (Ba3Co2Fe24O41) has attracted the most attention.2,5,10 Since the Co2Z ferrites have a very high sintering temperature of about 1250 °C, works to lower the sintering temperature of Co2Z are necessary. Considering the demand of keeping Contributing Editor: Michael E. McHenry a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.235 J. Mater. Res., Vol. 30, No. 18, Sep 28, 2015
the relatively high initial permeability of Co2Z at low sintering temperature, the Zn21 substitution was reported to be a useful way.2,3,10 In previous works, the BaCu (B2O5) (BCB) has been proven as a highly effective sintering aids to lower the sintering temperature of various materials.11–14 In this study, a small amount of BCB is utilized as the sintering aids to decrease the sintering temperature of (Co0.4Zn0.6)2Z ferrite. The i
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