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A low temperature fired Na2CaV4O12 ceramic was synthesized via a solid-state reaction route at a temperature range of 350–550 °C. The Thermal analysis confirmed the densification and melting temperature of Na2CaV4O12 to be 530 °C and 580 °C, respectively. Dielectric properties together with the electrical conductivity were characterized at a broad frequency and temperature range. A super-low relative permittivity of er = 7.72 and loss tangent of tanδ = 0.06 were obtained at 1 MHz at room temperature. A dielectric anomaly peak took place around 515 °C, which was associated with the phase transition from P4/nbm to P 4 ¯ b2. Ac impedance spectrum coupled with complex modulus plots unveiled the electrical conduction mechanism, which was dominated by the short-range movement of the charge carriers at low temperatures (T ≤ 220 °C) however long-range migration of charge carriers emerged at higher temperatures.

Effect of order/disorder transition on microwave dielectric characteristics is reported to develop a deeper understanding of structure-property relationship in spinel ceramics. Dense xLi4/3Ti5/3O4-(1-x)Mg2TiO4 (0.6≤x≤0.9) spinel ceramics were synthesized and characterized for structural and dielectric properties. The critical order/disorder structural transition was induced when x < 0.8, resulting in the ceramic crystallized into a primary cubic spinel phase, while when x > 0.8, the ceramic crystallized into a disordered face-centered cubic phase. The cation occupation caused this order-disorder transition, which directly influenced the variation in microwave dielectric properties. At x = 0.75 the maximum degree of order was achieved resulting in a maximum quality factor of 55,000 GHz and a near-zero τf = 2.9 ppm/oC. Dielectric properties decreased sharply after x = 0.8 when the disorder face-centered cubic phase started to crystallize. All the results indicated that cation ordering/disordering plays a critical role in determining the optimum microwave dielectric properties in spinel ceramics.

At extremely low temperatures, Ag2CaV4O12 was easily synthesized using the traditional solid-state approach. With a low relative permittivity (εr) of 7.52, a high quality factor (Q × f) of 48 800 GHz (f = 13.6 GHz), and a temperature coefficient of resonance frequency (τf) of −77.4 ppm/°C, dense ceramics sintered at 480 °C with outstanding microwave dielectric characteristics were attained. By combining with rutile TiO2, a composite ceramic with balanced microwave dielectric properties (τf = 3.2 ppm/°C, εr = 10.96, and Q × f = 49 081 GHz) was achieved. No chemical reaction between Ag2CaV4O12 and silver and aluminum occurred. All of the findings show that Ag2CaV4O12 has the potential to be used as dielectric resonances in wireless communication and as substrates in low-temperature cofired ceramics. Furthermore, the processing at an ultralow temperature of Ag2CaV4O12 shows that it is extraordinarily energy saving from the point of view of fabrication and might allow for room-temperature synthesis by combining with high-energy mechanical milling or sintering using a high pressure such as hot isostatic pressing (HIP), spark plasma sintering (SPS), and cold sintering (CS).

Three-dimensional printing-based additive manufacturing has emerged as a new frontier in materials science, with applications in the production of functionalized polymeric-based hybrid composites for various applications. In this work, a novel conceptual design was conceived in which an AC electric field was integrated into a commercial 3D printer (-based fused filament fabrication (FFF) working principle) to in situ manufacture hybrid composites having aligned ceramic filler particles. For this work, the thermoplastic poly lactic acid (PLA) was used as a polymer matrix while 10 vol% KNLN (K0.485Na0.485Li0.03NbO3) ceramic particles were chosen as a filler material. The degree of alignment of the ceramic powders depended upon print speed, printing temperature and distance between electrodes. At 210 °C and a 1 kV/mm applied electric field, printed samples showed nearly complete alignment of ceramic particles in the PLA matrix. This research shows that incorporating electric field sources into 3D printing processes would result in in situ ceramic particle alignment while preserving the other benefits of 3D printing.

Adjustment on resonance frequency stability against the sintering temperature of Sr3V2O8 was realized by adjusting the Sr:V mole ratio. Effects of Sr:V ratio on sintering behavior and dielectric properties of Sr3V2O8 were studied. The sintering temperature was sucessfully reduced to 950°C from 1150°C. With increasing vanadium content, both relative permittivity and quality factor decreased, while the temperature coefficient of resonance frequency shifted from positive to negative values. Especially, a near‐zero τf of −1.1 ppm/°C along with a low permittivity (εr) of 9.8 and a quality factor Q × f of 24 120 GHz was successfully achieved in Sr3‐yV2O8‐y ceramic (y = 0.6, sintered at 950°C). The wide compositional and processing adjustment window, favorable dielectric performances, and good chemical compatibility with silver render Sr3‐yV2O8‐y ceramics potential candidates in multilayer electronic devices.

As one of the candidates of low-temperature cofired ceramics (LTCC), the sintering behavior, dielectric properties, and silver chemical compatibility of NaCaVO4 were studied. The bulk ceramic samples were densified well at a low sintering temperature of 720 oC with an optimal bulk density of 2.87 g/cm3. Excellent microwave dielectric properties with a low relative permittivity er ~ 9.9, a high quality factor Q × f ~ 31,600 GHz, and a temperature coefficient of resonance frequency τf ~ -66.5 ppm/°C were achieved at 11.5 GHz. The far infrared reflectivity spectra revealed the intrinsic dielectric properties (relative permittivity of 8.34 and dielectric loss of 2.7×10-4) are comparable to the measured values. The absence of chemical reaction between NaCaVO4 and silver at firing temperature, evidenced by X-ray diffraction and energy dispersive spectroscopy indicated the potential prospect for LTCC application. Furthermore, the very low density of NaCaVO4 opens up an avenue for its potential applications in light-weight devices.

Ceramic matrix composites (CMCs) are a class of composite materials in which filler are incorporated within a ceramic matrix. As a result of filler addition to ceramic matrix, specific properties can be altered. There are various ways to manufacture ceramics and CMCs, mainly depending upon the filler material and the final application. One such property is a reduction in crack propagation. Although their constituents are brittle, CMCs have found their applications in the vast majority of the area, including space, refractories, energy storage, and automotive. This chapter considers classification and manufacturing CMCs. This chapter summarises state of the art for CMCs and their manufacturing techniques and lays the foundation for their micromachining.

Borates are promising candidates as dielectric substrate materials in low temperature cofired ceramics technology (LTCC) due to their relative low sintering temperatures and relative permittivities compared to their counterparts. However, synthesizing borates having single-phase is still challenging because of the volatility and hydrophilicity of boron resources. In this work, a compositional design was utilized to synthesize single-phase LiBGeO4 ceramics over a broad temperature range from 600 to 840 °C. Radio-frequency dielectric behaviours featured a strong temperature dependence, especially at high temperatures (>400 °C), which is related to the thermally activated polarizations. LiBGeO4 ceramic sintered at 820 °C has optimum microwave dielectric properties with the relative permittivity (er) of 6.28, a quality factor (Q × f) of 21,620 GHz, and a temperature coefficient of resonance frequency (τf) of -88.7 ppm/°C. LiBGeO4 also showed chemical inertness when cofired with silver (Ag), provided an evidence for its utilization in LTCC technology. Overall, this work provides a strategy for facile synthesis of phase pure borates, via the proposed two-step process to obtain stable boron resources.

Low-firing and temperature stable microwave dielectric ceramics of Ba2LnV3O11 (Ln = Nd, Sm) were prepared by solid-state reaction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the phase purity, crystal structure, sintering behavior, and microstructure. The XRD patterns indicated that Ba2LnV3O11 (Ln =Nd, Sm) ceramics belong to monoclinic crystal system with P21/c space group in the whole sintering temperature range (800-900 °C). Both ceramics could be well densified at 880 °C for 4 h with relative densities higher than 96%. The Ba2LnV3O11 (Ln =Nd, Sm) samples sintered at 880 °C for 4 h exhibited excellent microwave dielectric properties: er = 12.05, Q×f = 23,010 GHz, τf = –7.7 ppm/oC, and er = 12.19, Q×f = 27,120 GHz, τf = –16.2 ppm/oC, respectively. Besides, Ba2LnV3O11 (Ln =Nd, Sm) ceramics could be well co-fired with the silver electrode at 880 °C. This article is protected by copyright. All rights reserved.

Highly flexible lead free composite film having random distribution of ceramic filler was synthesized using Barium Titanate (BT) as a filler and inexpensive Thermoplastic Polyurethane (TPU) as a matrix. The results show that the 30 vol% BT-TPU composite has a dielectric constant of ~31 which is comparable to the expensive and difficult to produce PVDF based composites. With a breakdown field of 150 kV/mm, an energy density value of ~3 J/cm3 was estimated. These lead-free TPU based composites provide an alternative to PVDF based composites for energy storage applications.

Phase formation, crystal structure and dielectric properties of NaCa4V5O17 ceramics fabricated via a solid state reaction route at relatively low temperatures (780–860 °C) were investigated. NaCa4V5O17 crystallizes in a triclinic structure. Dielectric properties were measured based on the Hakki-Coleman post resonator method at microwave frequency. Specially, a specimen sintered at 840 °C demonstrated balanced dielectric properties with a permittivity er = 9.72, a quality factor Q×f = 51,000 GHz, and a temperature coefficient of resonance frequency τf = −84 ppm/°C. NaCa4V5O17 ceramics showed excellent chemical compatibility with Ag metal electrodes. Besides, the thermal stability of resonance frequency was effectively adjusted through formation of composite ceramics between NaCa4V5O17 and TiO2 and a near-zero τf ˜ 1.3 ppm/°C accompanied with er = 14.9 and Q×f = 19,600 GHz was achieved when 50% mol TiO2 was added. All the merits render NaCa4V5O17 a potential candidate for multilayer electronic devices.

In this paper, we present a method to create a highly sensitive piezoelectric quasi 1&ndash, 3 composite using a thermoplastic material filled with a piezoelectric powder. An up-scalable high-temperature dielectrophoresis (DEP) process is used to manufacture the quasi 1&ndash, 3 piezoelectric polymer-ceramic composites. For this work, thermoplastic cyclic butylene terephthalate (CBT) is used as a polymer matrix and PZT (lead zirconium titanate) ceramic powder is chosen as the piezoelectric active filler material. At high temperatures, the polymer is melted to provide a liquid medium to align the piezoelectric particles using the DEP process inside the molten matrix. The resulting distribution of aligned particles is frozen upon cooling the composite down to room temperature in as little as 10 min. A maximum piezoelectric voltage sensitivity (g33) value of 54 &plusmn, 4 mV&middot, m/N is reported for the composite with 10 vol% PZT, which is twice the value calculated for PZT based ceramics.

Piezoelectric composites made from soft and hard lead zirconium titanate (PZT) particles as filler and an epoxy as the matrix were prepared by dielectrophoresis and studied for their piezoelectric properties. It was found that the dielectric constant of the piezoelectric filler plays a significant role in determining the final piezoelectric properties of the composites. Composites with lower dielectric constant for the PZT filler material showed better piezoelectric properties compared to the composites with high dielectric constant filler. This can be ascribed to a more efficient poling of the piezoelectric filler particles. The aging behaviour of these composites was compared to that reported for monolithic ceramics.

A Ca5Ni4(VO4)6 low loss microwave dielectric ceramic with A site deficient garnet structure was prepared via the conventional solid state reaction method. Ca5Ni4(VO4)6 sintered at 980 °C for 4 h to a relative density of 96.2% exhibits favorable microwave dielectric properties such as a permittivity of 10.9, a Q×f value of 96,500 GHz, and a τf value of −63.6 ppm/°C. Its large negative τf could be compensated by forming a solid solution with LiCa2Mg2V3O12, that led to improved properties with a near-zero τf=−3.7 ppm/°C, er=10.2, Q×f=59,300 GHz for 0.8Ca5Ni4(VO4)6−0.2LiCa2Mg2V3O12 after sintering at 955 °C for 4 h. Further on, 0.8Ca5Ni4(VO4)6−0.2LiCa2Mg2V3O12 proved to be chemically compatible with Ag electrodes, so it might be a possible candidate for LTCC applications.

A Li4WO5 ceramic with rock salt structure was prepared by the solid-state reaction method and its microwave dielectric properties was demonstrated for the first time. It could be well densified at relatively low sintering temperature (∼890 °C). XRD and DTA analysis revealed a phase transformation from cubic to orthorhombic occured at 700 °C. Excellent microwave dielectric properties with a near-zero temperature coefficient of resonant frequency ∼−2.6 ppm/°C, a relative permittivity ∼8.6 and a quality factor ∼23,100 GHz (at 11.0 GHz) was obtained. Li4WO5 was found to be chemically compatible with silver powders when sintered at 890 °C. All the results indicate that the Li4WO5 ceramic is a promising candidate as a base material in low temperature cofired ceramic technology.