Dielectric Losses of Microwave Ceramics Based on Crystal Structure

Abstract

So far, many microwave dielectric materials have been investigated for a range of telecommunication applications. In dielectrics, the three main dielectric properties are quality factor (Q), dielectric constant and temperature coefficient of resonant frequency. Among these, the most essential dielectric property is Q. More specifically, Q is the inverse of the dielectric loss (tanδ); thus Q = 1/tanδ. There are two kinds of losses: those depending on crystal structure and losses due to external factors. The former is intrinsic losses such as ordering, symmetry, and phonon vibration. The latter is extrinsic losses due to factors such as grain size, defects, inclusions and distortion. In this chapter, the authors present the origin of dielectric losses based on the crystal structure. An ideal and well-proportional crystal structure constitutes a low loss material. Most dielectric materials are paraelectrics with inversion symmetry i and high symmetry. In general, it is believed that ordering gives rise to a high Q, on which many researchers are casting doubt. In the case of complex perovskites, the symmetry changes from cubic to trigonal. Ordering and symmetry should be compared with the structure. In this chapter, three essential conditions for the origin of high Q such as high symmetry, compositional ordering and compositional density are presented.

5G planar branch line coupler design based on the analysis of dielectric constant, loss tangent and quality factor at high frequency

“…Generally, this behavior can be explained by the characteristics of the ε r that is influenced by ionic or electronic polarization, which generates α d in the presence of electromagnetic wave 27 . The increasing value of ε r provides a higher α d value as the electric field intensity inside the dielectric layer increases 23 .…”

Analysis of the crystalline structure of polymorphic modifications of compound Ва6Ta2O11

“…The PDF-2 database for 2004 contains three diffraction spectra of the Ва 6 Ta 2 O 11 compound (Table 1). A fragment of the phase diagram of the BаO-MgO-Ta 2 O 5 system given in [4] is shown in Fig. 1, where it is indicated that the compound is a metastable phase and can be used as a microwave dielectric [1,4].…”

“…A fragment of the phase diagram of the BаO-MgO-Ta 2 O 5 system given in [4] is shown in Fig. 1, where it is indicated that the compound is a metastable phase and can be used as a microwave dielectric [1,4].…”

“…According to [4], the dielectric properties (dielectric figure of merit) is closely related to their crystal structure. There is also information that this compound is a metastable phase [4] and crystallizes in the [NH 4 ] 3 FeF 6 [3] structural type [3].…”

Synthesis and Microwave Dielectric Properties of BBSZ-Zinc Silicate Based Material for LTCC Applications

“…5 Several silicate-based materials such as Mg 2 SiO 4 , MgSiO 3 , ZrSiO 4 , Cu-doped Mg 2 SiO 4 , and Zn 2 SiO 4 are well known for substrate application at microwave frequency range. [6][7][8][9] However, most of these materials cannot be used for LTCC because of their high sintering temperature. There are some known strategies for reducing the sintering temperature of these materials, which include the addition of low-melting-point glasses or the addition of lowmelting-point oxides, which can be employed in order to use these materials for LTCC application.…”