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The crystal structure, lattice vibration and microwave dielectric properties of 3CaO·2SiO 2 · x CaF 2 ceramics were investigated in this work. With the increasing of x value, the crystal structure of 3CaO·2SiO 2 · x CaF 2 ceramics transfers from rankinite (Ca 3 Si 2 O 7) to cuspidine (Ca 4 Si 2 O 7 F 2). The increase of the vibration energy and shrinkage of [SiO 4 ] tetrahedral unit hampers the ionic polarization and thus reduces relative permittivity (ε r). The enlarged FWHM of the Si–O stretching peak reflects a more drastic anharmonic lattice vibration, resulting in a lower quality factor (Q × f value). The Raman shift of O/F–Ca–O/F bending peak is positively correlated with the temperature coefficient of resonant frequency (τ f). The microwave dielectric properties of ε r and Q × f value (∼@11 GHz) ranging from 7.89 to 8.42, and 21805–46098 GHz, respectively. The stable complex permittivity (ε r ∗) in the frequency range of 20–110 GHz indicates that the fluoride cuspidine ceramics could be a promising candidate for microwave device applications. [ABSTRACT FROM AUTHOR]

In this work, 4CuO-TiO2-2Nb2O5 (CTN) composite oxide was added to ZnAl2O4 as sintering aid. XRD analysis revealed that trace amount of new phases formed in the ceramic samples with CTN, which might promote the low temperature sintering of ZnAl2O4 ceramics. The sample with 2 wt% CTN addition sintered at 1125 °C can achieve the highest thermal conductivity of 8.6 W/m·K and the lowest microwave dielectric loss of 3.59 × 10−4. The sintering temperature and thermal conductivity of ZnAl2O4 ceramics decreased while the dielectric constant and loss increased with the increase of the CNT contents. ZnAl2O4 ceramics can be sintered at a low temperature of 950 °C with the CTN content increasing to 10 wt%, which make it a potential material for the low temperature co-fired ceramics (LTCC) application. [ABSTRACT FROM AUTHOR]

The CaTi (1-x) (Al 0.5 Nb 0.5) x SiO 5 (0 ≤ x ≤ 0.1) ceramics were prepared by the conventional solid-state method. Al and Nb co-doping improved the high temperature stability of the CaTiSiO 5 material and no obvious phase transition was found at temperature up to 623 K for x ≥ 0.03. A dielectric constant of 53, dielectric loss of 0.001, resistivity of 8.5 × 1013 Ω cm, and breakdown strength of 1064.7 kV/cm was obtained for the CaTi 0.97 (Al 0.5 Nb 0.5) 0.03 SiO 5 ceramics at room-temperature. The dielectric constant is stable over a wide temperature range and a resistivity of 9.0 × 1010 Ω cm could still be achieved up to 573 K. The P-E loops measurements showed that energy storage efficiencies of 96% and 88.6% could be obtained at room-temperature and 453 K, respectively, for the CaTi 0.97 (Al 0.5 Nb 0.5) 0.03 SiO 5 ceramics. The excellent dielectric properties at elevated temperature indicate that titanite based ceramics stabilized by Al and Nb co-doping could be promising candidates for high temperature ceramic capacitors application. • The pure high-temperature monoclinic A2 1 /a phase of doped CaTiSiO 5 was obtained. • Co-doping of Al3+ and Nb5+ ions stabilizes the crystal phase at elevated temperatures up to 623 K. • Stable dielectric constant and high resistivity are achieved over a wide temperature range up to 573 K. [ABSTRACT FROM AUTHOR]

In this work, (Li, Nb) co-doped TiO 2 ceramics (LNTO x , x < 0.1), were synthesized through a conventional solid state reaction method. As revealed by X-ray diffraction (XRD) spectra, all LNTO ceramics exhibited pure tetragonal rutile structure. The LNTO 0.01 ceramic showed a colossal permittivity over 7000 and a low dielectric loss (tg δ < 0.06) in a wide frequency range of 102 Hz–107 Hz. The dielectric spectra under DC biases were tested at different temperatures. The experimental data could fit the modified Debye equation well. It was found that there are multiple dielectric polarization mechanisms in LNTO ceramics including space charge polarization, relaxor-type relaxation, polaron hopping and dipole polarization related with localized electrons. [ABSTRACT FROM AUTHOR]

The (Ba0.97− xCa0.03Dy x)(Ti0.98Mg0.02)O3 (BCTDM-nano) ( x = 0, 0.005, 0.01, 0.02, 0.03) ceramics with nanosized grains were synthesized through a solid-state reaction method. The influence of Dy3+ substitution on the lattice and electrical properties were investigated. The X-ray diffraction and Raman scattering analyses demonstrate that the Dy3+ ions could modulate the doping position of Ca2+ and Mg2+ and affect the tetragonality and defects in BaTiO3 matrix. The maximum dielectric constant was increased up to 2500 for the sample with x = 0.01. A high dielectric breakdown strength of 239 kV cm−1 was obtained at x = 0.01. The high grain boundary resistance resulted from a charge compensation by Dy doping benefits the improved dielectric breakdown strength. [ABSTRACT FROM AUTHOR]

In this study, a colossal permittivity up to 3800 and a low dielectric loss of 0.11 at 1 kHz have been obtained from the (Li, In) co-doped ZnO ceramic [Zn (1−2x) (Li, In) x O] when x was 0.5%. Electric modulus spectroscopy and impedance analysis were used to investigate the origin of its high permittivity. Two relaxation peaks and a dielectric anomaly were observed in the temperature range of 293–363 K. According to the Debye relaxation theory, the low- and high-temperature relaxation peaks with activation energies of 0.09 eV and 0.29 eV, have been attributed to the hopping of singly and doubly charged oxygen vacancies, which are created by lithium and indium ions doping and oxygen deficiency during sintering process. After thermal treatment in an oxidizing atmosphere, the peaks related to the singly and doubly charged oxygen vacancies disappear and the permittivity reduces to ∼460 at room-temperature. From the X-ray photoelectron spectra (XPS), the concentrations of oxygen vacancies decrease after the O 2 -annealing process. The results reveal that the oxygen defects would be the main origin of the colossal permittivity of co-doped ZnO at room-temperature range. [ABSTRACT FROM AUTHOR]

A compact diplexer is implemented in Low‐Temperature‐Cofired‐Ceramic (LTCC) technology and consists of six coupled substrate‐integrated‐waveguide (SIW) cavity resonators stacked in two layers. No transmission‐line based junction is used. The couplings between the cavities are achieved through both SIW irises and slots placed in metal layers. The diplexer has two third‐order filtering channels, centred at 2.7 and 3.3 GHz with 120 MHz bandwidths. The overall size of the diplexer is 27.74 mm (2.3λg at 3 GHz) × 10.4 mm (0.86λg at 3 GHz) × 0.84 mm, achieved by using an LTCC material of a high dielectric constant of 68. Simulations and measurements are in good agreement to demonstrate a compact diplexer based on an all‐resonator structure using high dielectric constant LTCC material. [ABSTRACT FROM AUTHOR]

Mg and Mn co-doped LaGa0.7-xMgxMn0.3O3 (x = 0, 0.05, 0.10, 0.15) ceramics were prepared by a solid-state reaction method. The electrical properties of the LaGa0.7-xMgxMn0.3O3 ceramics were studied in detail by dielectric spectra, impedance spectra, and I-V characteristic analysis. Colossal permittivity up to 104 could be obtained across the frequency range up to 104 Hz. The impedance analysis of the co-doped LaGaO3 ceramics indicated that the Mott's variable range hopping (VRH) polarization should be the main origin of colossal permittivity. Mg and Mn co-doping suppressed the formation of Mn3+ and enhanced the VRH polarization, resulting in increased permittivity. Partial localization of electrons by Mg reduced the long-range electron hopping and led to the decrease in dielectric loss. [ABSTRACT FROM AUTHOR]

This work reports a novel wireless microfluidic biosensor based on low temperature co-fired ceramic (LTCC) technology. The wireless biosensor consists of a planar spiral inductor and parallel plate capacitor (LC) resonant antenna, which integrates with microchannel bends in the LTCC substrate. The wireless response of the biosensor was associated to the changes of its resonant frequency due to the alteration in the permittivity of the liquid flow in the microchannel. The wireless sensing performance to different organic liquids with permittivity from 3 to 78.5 was presented. The measured results are in good agreement with the theoretical calculation. The wireless detection for the concentration of glucose in water solution was investigated, and an excellent linear response and repeatability were obtained. This kind of LC wireless microfluidic sensor is very promising in establishing wireless lab-on-a-chip for biomedical and chemical applications. [ABSTRACT FROM AUTHOR]

The terahertz (THz) dielectric constant (ε r ') and dielectric loss tangent (tan δ) of the commercial LTCC materials (Ferro A6M and DuPont 951), Al 2 O 3 (ceramic and single crystal), AlN and β-Si 3 N 4 ceramics were measured using a vector network analyzer (VNA) over the frequency range of 140–220 GHz and a time-domain spectrometer (TDS) from 0.2 to 1.0 THz. The results from the two instruments are compared with the literature and show good agreement and consistency. For Ferro A6M, ε r ' = 6.06, tan δ = 0.012 at 1.0 THz. For DuPont 951, ε r ' = 7.67, tan δ = 0.097 at 1.0 THz. For Al 2 O 3 ceramic and single crystal, the measured THz dielectric properties are consistent with the reported works. The dielectric constant of AlN (ε r ' = 8.85) and β-Si 3 N 4 (ε r ' = 8.41) ceramics in the THz region is a little lower than those reported for the MHz to GHz region. These results provide valuable and much needed reference information for device designers and material scientists. [ABSTRACT FROM AUTHOR]

Dielectric properties of pure phase BaTi 0.99 (Nb 0.5 Ga 0.5 ) 0.02 O 3 ceramics, prepared via a conventional solid-state method, have been studied in the frequency range 0.01 Hz–10 MHz, at temperatures −130 °C to 200 °C. Colossal dielectric constant, ε r ~2×10 5 , and low dielectric loss, tan δ ~0.05 at 1 kHz have been obtained. The permittivity showed weak frequency dependency in a broad range of frequency from 1 Hz to 30 kHz and less than ±20% capacitance deviation over the temperature range from 243 to 358 K. The AC impedance spectroscopy analysis indicated three relaxation mechanisms, the electrode interfacial polarization, internal barrier layer capacitor effect and hopping polaron polarization contributed to the colossal dielectric constant. [ABSTRACT FROM AUTHOR]