Microwave dielectric properties

Marand, E., Baker, K.R. and Graybeal, J.D., Comparison of reaction-mechanisms ofepoxy-resins undergoing thermal and microwave cure from in situ measurements of microwave dielectric-properties and infrared-spectroscopy, Macromolecules, 1992, 25, 2243. 

Figure 5.9 Planar nonlinear dielectric based thin film varactor structure (top) and planar microstrip resonator with capacitive gap. The microwave dielectric properties of the varactor structure are measured in a flipchip configuration of both substrates with the narrow (few microns) capacitive gap of the varactor structure being placed in the center of the large (500 microns) capacitive gap of the resonator structure (from [16]).

With the progress in microwave telecommunication technology, dielectric materials have come to play an important role in the miniaturization and compactness of microwave passive components. The dielectric materials available for micro-wave devices are required to have predictable properties with respect to a high dielectric constant (K), high quality factor (Qf), and small temperature coefficient of resonant frequency (TCP). Numerous microwave dielectric materials have been prepared and investigated for their microwave dielectric properties and for satisfying these requirements. In particular, complex perovskite compounds A(B,B )03... 

Several kinds of dielectric materials have been widely investigated to improve their properties and to meet the requisites of high dielectric constant (K), low dielectric loss (Qf), and low TCF. Based on these requisites, complex perovskite compound, A(B,B )03, was extensively studied from the viewpoint of the compositional and structural dependence on their microwave dielectric properties. Among them, much attention has been paid to lead-based ceramics with complex perovskite structures because of their superior dielectric properties required for microwave devices. 

As mentioned in a previous section, the dielectric properties are largely affected by the structural characteristics of solid solution. Since the bond valence is a function of bond strength and bond length," the structural characteristics largely depend on bond valence. Therefore the dielectric properties could effectively be estimated by bond valence. Let s examine the effects of A-site and B-site bond valence on the microwave dielectric properties of lead-based complex perovskite compounds. 

Food materials are poor electric insulators and can store and dissipate energy when exposed to microwaves. Dielectric properties describe an interaction of an electromagnetic field with non- or low-conducting matter. The dielectric properties data are very limited in literature and usually available only for a few foods or food components. Wang et al. (2008), Tanaka et al. (2008), and Liao et al. (2001, 2002, 2003) have conducted experiments to get a better understanding of the dielectric properties of various food products. The dielectric properties of some food materials are shown in Table 3.1 (Regier and Schubert, 2001). 

S. Nishigaki, H. Kato, S. Yano, R. Kamimure, Microwave dielectric properties of (Ba, Sr)0-Sm203-Ti02 ceramics. Am. Ceram. Soc. Bull. 66 (1987) 1405-1410. 

K. W. Kang, H. T. Kim, M. Lanagan, T. Shrout, Low-temperature sintering and microwave dielectric properties of CaTii-x(Feo.5Nbo.5)x03 ceramics with B2O3 addition. Mater. Res. Bull. 41 (2006) 1385-1391. 

R. Umemura, H. Ogawa, A. Yokoi, H.Ohsato, A. Kim, Low-temperature sintering-microwave dielectric property relations in Ba3(V04)2 ceramic, J. Alloys Compd. 424 (2006) 388-393. 

MICROWAVE DIELECTRIC PROPERTIES OF (l-x)(Mgo6Zno.,)o.95Coo.o5TiOrxSrTi03 CERAMIC SYSTEM... 

Microwave Dielectric Properties of (1-x)(Mgo 0Zno,4)o.95Coo.o5TiO3-xSrTiO3 Ceramic System... 

Table 1 Microwave dielectric properties of (l-x)(Mgo,6Zno.4)o 95Coo.o5Ti03-xStTi03 ceramic system sintered at 1250"C for4h...

---