Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and y500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The commercially available LTCCs, low loss glass phases and researched novel materials are listed with properties and references. Additionally, their high frequency and thermal performances are compared with the other substrate material options such as high sintering temperature ceramics and polymers, and further improvements in materials' development required are discussed.

In addition to the constant demand of low-loss dielectric materials for wireless telecommunication, the recent progress in the Internet of Things (IoT), the Tactile Internet (fifth generation wireless systems), the Industrial Internet, satellite broadcasting and intelligent transport systems (ITS) has put more pressure on their development with modern component fabrication techniques. Oxide ceramics are critical for these applications, and a full understanding of their crystal chemistry is fundamental for future development. Properties of microwave ceramics depend on several parameters including their composition, the purity of starting materials, processing conditions and their ultimate densification/porosity. In this review the data for all reported low-loss microwave dielectric ceramic materials are collected and tabulated. The table of these materials gives the relative permittivity, quality factor, temperature variation of the resonant frequency, crystal structure, sintering temperature, measurement frequency and references. In addition, the methods commonly employed for measuring the microwave dielectric properties, important from the applications point of view, factors affecting the dielectric loss, methods to tailor the dielectric properties and materials for future applications, are briefly described. The data will be very useful for scientists, industrialists, engineers and students working on current and emerging applications of wireless communications.

Composite technology, where a novel artificial material is fabricated by combining, for example, ceramic and polymer materials in an ordered manner or just by mixing, was earlier used widely for sonar, medical diagnostics, and NDT purposes. However, in recent decades, large numbers of ceramic-polymer composites have been introduced for telecommunication and microelectronic applications. For these purposes, composites of 0-3 connectivity (a three-dimensionally connected polymer phase is loaded with isolated ceramic particles) are the most attractive from the application point of view. Composites of 0-3 connectivity enable flexible forms and very different shapes with very inexpensive fabrication methods including simply mixing and molding. In this brief review, we gather together the research carried out within 0-3 ceramic-polymer composites for microwave substrates, also including embedded capacitor, inductor, or microwave-absorbing performances.

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Li2ATi3O8 (A=Mg, Zn) ceramics are prepared by the conventional solid‐state ceramic route, and the phase purity, microstructure, and microwave dielectric properties are investigated. Li2MgTi3O8 ceramics show ɛr=27.20, Qu×f=42 000 GHz, and τf=(+) 3.2 ppm/°C, and Li2ZnTi3O8 ceramics have ɛr=25.6, Qu×f=72 000 GHz, and τf=(−) 11.2 ppm/°C, respectively, when sintered at 1075°C/4 h.

Raman spectroscopy was employed to evaluate the crystal structure and phonon modes of chemically substituted Ba(RE 1/2 Nb 1/2 )O 3 microwave ceramics (RE ) La, Nd, Sm, Gd, Tb, and Y). It was verified that these materials could be divided into tetragonal (ceramics with RE ) Y, Tb, and Gd) and orthorhombic (RE ) Sm, Nd, and La) structures. Lorentzian lines were used to fit the spectra, which presented 9 bands for the first group and 23 bands for the second group of ceramics. The position and width of the phonon modes were determined, and were correlated to the ionic radii and tolerance factors for the different atoms substituted in the B′-site. It is believed that simple rotational distortions of the oxygen octahedra led to the occurrence of structures other than cubic, which is very difficult to detect by X-ray diffraction or even spectroscopic techniques.