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.

Polymer–Ceramic Composites of 0–3 Connectivity for Circuits in Electronics: A Review

The BiVO4 material has attracted much attention in recent years due to its active photocatalytic properties under visible light, bright yellow color as a nontoxic pigment, and its high relative permittivity (er) and Qf (quality factor, Q × resonant frequency, f) as a potential microwave dielectric ceramic. In this review, we introduce the origin, synthesis, crystal structure and phase transitions of the four polymorphic phases of BiVO4: orthorhombic (pucherite), zircon (dreyerite), scheelite monoclinic (clinobisvanite) and scheelite tetragonal. We then precis recent studies on doped BiVO4 ceramics in terms of A site, B site and A/B site complex substitutions. Low sintering temperature (<800 °C) and high er values could be obtained in some solid solution ceramics and near zero temperature coefficient of resonant frequency (TCF/τf) values could be achieved in layered or granulated particle composite ceramics. Besides, a series of temperature stable high er microwave dielectric ceramics can also be obtained for many co-fired composite ceramics, such as BiVO4–TiO2, and BiVO4–TiO2–Bi2Ti4O11. The high er, high Qf value, low sintering temperature and chemical compatibility with some base metals suggest that BiVO4-based materials are strong candidates for both LTCC and other microwave device applications in current 4G and future 5G technologies.

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BiVO4 based high k microwave dielectric materials: a review

A novel functional nanoconducting composite from polyvinyl chloride reinforced graphite-copper nanoparticles (PVC/GCu) was fabricated in order to produce a material suitable for electromagnetic interference (EMI) shielding applications. The microstructure of the nanocomposites was investigated by means of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The thermal stability of the nanocomposites could improved with the incorporation of GCu nanoparticles. The electrical conductivity increases with increasing GCu content within composites. The percolation threshold of composites is low of about 2 wt.%. Hall-effect studies indicate that increase in GCu content in the composites causes increase in carrier concentration, mobility of the carriers and the composites behave as n-type semiconductor. The nanocomposites showed a high dielectric constant and a high dissipation factor in the frequency range of 1-20 GHz which makes it useful in charge storing and decoupling capacitors applications. The EMI shielding effectiveness (SE) of the PVC/GCu nanocomposites was tested over a frequency range of 1-20 GHz, and 22-70 dB shielding efficiency was obtained for the composites, suggesting that they may be used as an effective lightweight EMI shielding material in aerospace and radar evasion applications.

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New electromagnetic wave shielding effectiveness at microwave frequency of polyvinyl chloride reinforced graphite/copper nanoparticles

The flat panel display (FPD) market has been experiencing a rapid transition from liquid crystal (LC) to organic light emitting diode (OLED) displays, leading, in turn, to the accelerated commercialization of OLED televisions already in 2013. The major driving force for this rapid change was the adaptation of novel oxide semiconductor materials as the active channel layer in thin film transistors (TFTs). Since the report of amorphous-InGaZnO (a-IGZO) semiconductor materials in 2004, the FPD industry has accelerated the development of oxide TFTs for mass-production. In this review, we focus on recent progress in applying electro-ceramic materials for oxide-semiconductor thin-film-transistors. First, oxide-based semiconductor materials, distinguished by vacuum or solution processing, are discussed, with efforts to develop high-performance, cost-effective devices reviewed in chronological order. The introduction and role of high dielectric constant - reduced leakage gate insulators, in optimizing oxide-semiconductor device performance, are next covered. We conclude by discussing current issues impacting oxide-semiconductor TFTs, such as field effect mobility and device stability and the proposed directions being taken to address them.

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Overview of electroceramic materials for oxide semiconductor thin film transistors

Surface chemical analysis on the carbon-doped mesoporous TiO2 photocatalysts after post-thermal treatment: XPS and FTIR characterization

High permittivity and low-loss SrTiO3/Ni0.8Zn0.2Fe2O4 (STO/NZO) composites with concrete-like morphology were prepared through hybrid processing route. The dielectric properties in the low-frequency range (100 Hz–1 MHz) follow the rule of Maxwell–Wagner interfacial polarization. The dielectric and magnetic properties in the high-frequency range (10 MHz–1 GHz) exhibit a well integration of dielectric and magnetic properties in the composites with low dielectric and magnetic losses. The STO/NZO composites show good dielectric properties and magnetic properties with low loss in high-frequency to microwave-frequency range. The results show that this kind of magnetic–dielectric composites can be used in high-frequency communications for the capacitor–inductor integrating devices such as electromagnetic interference filters and antennas.

Microstructure and Electromagnetic Properties of SrTiO3/Ni0.8Zn0.2Fe2O4 Composites by Hybrid Process

Multifunctional dielectric composites with electromagnetic and flexible properties for RF applications were investigated. A kind of low loss flexible dielectric and magnetic composite with SrTiO3 (STO) ultrafine particles and NiZn ferrite (NZO) ultrafine particles embedded in a Thermoplastic Polyolefin Elastomer (POE) matrix was fabricated using the extrusion technology. The dielectric and magnetic properties of the as-prepared composites with different volume fraction of ceramic fillers were studied. The results indicate that when the volume of the ceramic fillers is fixed, the permittivity of the composites increase while the dielectric loss, permeability and magnetic loss decrease with the increasing of the ratio of STO to NZO. The cut-off frequencies of the composites are all above 1 GHz. The good frequency stability of the electromagnetic properties within a wide frequency range was observed. All the composites show very good flexibilities. With the increasing of the volume fraction of ceramic fillers, the tensile strength and elongation decrease. The obtained multifunctional flexible magnetic-dielectric composites are good candidates for the applications of the capacitor-inductor integrating devices in RF communications such as electromagnetic interference filters and antennas.

Multifunctional SrTiO3/NiZn ferrite/POE composites with eletromagnetic and flexible properties for RF applications

Hexagonal BaTiO3/Ni0.8Zn0.2Fe2O4 composites with giant dielectric constant and high permeability

The coexistence of Li2MoO4 (LMO) and Ni0.5Zn0.5Fe2O4 (NZO) has been proven and their low-temperature-sintered magneto-dielectric composites (1−x)LMO–xNZO (volume fraction factor x = 0.1, 0.3, 0.5, 0.7) were prepared by the conventional solid-state reaction method and were sintered below 700°C. It is found that the optimal sample (x = 0.5) has good and relatively stable magneto-dielectric performance in the frequency range from 10 MHz to 1 GHz with permittivity between 7.14 and 6.84, dielectric loss tangent between 0.09 and 0.02, and permeability between 5.23 and 3.30, magnetic loss tangent between 0.06 and 0.65, respectively. Furthermore, the verified chemical compatibility with silver indicates that the LMO–NZO ceramics are potential for low-temperature cofired ceramic application and their multifunctional magneto-dielectric properties also make them for potential applications in electronic devices.

Low-Temperature Sintering Li2MoO4/Ni0.5Zn0.5Fe2O4 Magneto-Dielectric Composites for High-Frequency Application

The influence of BaCu(B2O5) (BCB) addition on the sintering temperature and microwave dielectric properties of ZnO-2TiO2-Nb2O5 (ZTN) ceramic has been investigated using dilatometry, x-ray diffraction, scanning electron microscopy, and microwave dielectric measurements. A small amount of BCB addition to ZTN can lower the sintering temperature from 1100°C to 900°C. The reduced sintering temperature was attributed to the formation of the BCB liquid phase. The ZTN ceramics containing 3.0 wt.% BCB sintered at 900°C for 2 h have good microwave dielectric properties of Q × f = 19,002 GHz (at 6.48 GHz), e
 r = 45.8 and τ
 f
  = 23.2 ppm/°C, which suggests that the ceramics can be applied in multilayer microwave devices, provided that Ag compatibility exists.

Haibo Yang

Papers

Microstructure and Electromagnetic Properties of SrTiO3/Ni0.8Zn0.2Fe2O4 Composites by Hybrid Process

Multifunctional SrTiO3/NiZn ferrite/POE composites with eletromagnetic and flexible properties for RF applications

Hexagonal BaTiO3/Ni0.8Zn0.2Fe2O4 composites with giant dielectric constant and high permeability

Low-Temperature Sintering Li2MoO4/Ni0.5Zn0.5Fe2O4 Magneto-Dielectric Composites for High-Frequency Application

Microwave Dielectric Properties of ZnO-2TiO2-Nb2O5 Ceramics with BaCu (B2O5) Addition