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This study synthesized two novel middle- ε r Ln 3 NbO 7 (Ln = Nd, Sm; named NNO and SNO) microwave dielectric ceramics through the classic solid-state process. The results of XRD and Rietveld refinement show that NNO and SNO ceramics formed pure phases with the space group Cmcm (63) and C222 1 (20), respectively. The properties of Ln-O and Nb–O bonds of NNO and SNO ceramics were calculated based on the P–V–L theory. The Nb–O bonds positively affect the crystal structure stability of the two ceramics. The optimum microwave dielectric properties were obtained (NNO: ε r = 31.61, Q·f = 6,615 GHz (at 6.10 GHz), and τ f = −455.70 ppm/°C; SNO: ε r = 34.55, Q·f = 11,625 GHz (at 5.77 GHz) and τ f = 72.59 ppm/°C) when the samples sintered at 1550 °C. Notably, SNO ceramic shows a low dielectric loss and medium dielectric constant, and the opposite τ f of NNO and SNO ceramics provide the possibility to fabricate microwave dielectric devices with good temperature stability. [ABSTRACT FROM AUTHOR]

Ni 3 (PO 4) 2 as microwave dielectrics was investigated in terms of sintering behavior and microwave dielectric properties and synthesized using the solid-state sintering method. X-ray diffraction (XRD) data revealed that the Ni 3 (PO 4) 2 ceramics belong to the monoclinic structure with the P2 1 /c (#14) space group. The sintering behavior analysis confirmed that the sample reached a dense state at 1200 °C. It's permittivity (ε r) and quality factor (Q × f) possess distinct density-dependent features. The admirable Q × f of 83,430 GHz (at 10.21 GHz) was accomplished coupled with a low ε r of 6.23 and temperature coefficient of resonant frequency (τ f) of −24.63 ppm/°C in Ni 3 (PO 4) 2 ceramic when sintering at 1200 °C for 2 h. Thus, it is a promising candidate for microwave dielectrics with low loss and low permittivity. The dielectric properties were discussed using the chemical bond theory, and their chemical bond features were quantified. The results confirmed the significance of P–O bonds in the microwave dielectric response of Ni 3 (PO 4) 2 ceramic. [ABSTRACT FROM AUTHOR]

A novel Cu 3 (PO 4) 2 as microwave dielectrics was investigated in terms of sintering behavior and microwave dielectric properties. Samples were prepared using the solid-state sintering method. XRD data indicates that the Cu 3 (PO 4) 2 ceramic possesses a triclinic structure and belongs to the space group of P-1 (No. 2). Its microstructure was observed using a scanning electron microscope. Results confirmed that a dense ceramic was obtained at 900 °C. The permittivity and quality factor of Cu 3 (PO 4) 2 ceramics possess distinct density-dependent properties. A low permittivity (ε r) of 7.33 coupled with Q × f of 86,753 GHz (at 10.18 GHz) and τ f of −33.80 ppm/°C was obtained in the dense Cu 3 (PO 4) 2 ceramic at 900 °C for 2 h. The Cu 3 (PO 4) 2 ceramic exhibits well compatibility with Ag. Accordingly, it is a promising candidate for microwave materials with low permittivity and low loss. The microwave dielectric properties were discussed from the viewpoint of chemical bond theory. The qualified chemical bond features indicate the major contributions of P–O chemical bonds in the microwave dielectric response of the Cu 3 (PO 4) 2 ceramic. [ABSTRACT FROM AUTHOR]

This work prepared a new type of Ce 2 [Zr 1- x (Al 1/2 Nb 1/2) x ] 3 (MoO 4) 9 (CZ 1- x (AN) x M) (x = 0.02–0.10) microwave dielectric ceramics through the solid-phase process. CZ 1- x (AN) x M ceramics exhibited low dielectric constant, ultra-low dielectric loss, and near-zero resonant frequency temperature coefficient, which is suitable for 5 G technology. The effects of (Al 1/2 Nb 1/2)4+ replacing Zr4+ on the sintering characteristics, crystal structure, and microwave dielectric properties of Ce 2 Zr 3 (MoO 4) 9 (CZM) ceramics were studied systematically. In this work, CZ 1- x (AN) x M could form a pure crystal structure in the whole doping range according to the X-ray diffraction pattern. The crystal cell parameters of the ceramics were confirmed by Rietveld refinement analysis. Furthermore, the surface morphology of CZ 1- x (AN) x M sintered at the optimum sintering temperature was studied by scanning electron microscopy. Some internal parameters of the ceramics were calculated and analyzed by employing the P-V-L theory. The theoretical loss was acquired by employing an infrared reflection spectrometer. When x was 0.04 and the sintering temperature was 850 ℃, the best properties were achieved, including ε r = 10.54, Q·f = 91,476 GHz (at 9.55 GHz), and τ f = − 8.95 ppm/℃. This work studied the relationship between lattice vibration and microwave dielectric properties and discussed the influence of ion doping on microwave dielectric properties from the perspective of chemical bonds, laying a theoretical foundation for related research. [Display omitted] • The intrinsic factor of the permittivity was analyzed by IR reflectance spectroscopy. • The cell parameters were obtained through the Rietveld refinement method. • The effects of (Al 1/2 Nb 1/2)4+ the properties were explored based on the P-V-L theory. • Excellent properties including, ε r = 10.54, Q·f = 91,476 GHz, and τ f = − 8.95 ppm/℃. [ABSTRACT FROM AUTHOR]

Ce 2 [Zr 1−x (Ca 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1−x (CS) x M) (x = 0.02–0.10) ceramics were prepared by the conventional solid-state reaction method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips–Van Vechten–Levine (P–V–L) theory. Phase composition and microstructures were evaluated by scanning electron microscopy and X-ray diffraction patterns. Lattice parameters were obtained by Rietveld refinements based on XRD data. Excellent properties for Ce 2 [Zr 0.96 (Ca 1/3 Sb 2/3) 0.04 ] 3 (MoO 4) 9 ceramic sintered at 775 °C: ε r = 10.68, Q × f = 85,336 GHz and τ f = −7.58 ppm/°C were achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] The lotus seedpod-based activated carbon (LSAC) is derived from pyrolysis of lotus seedpod as biomass carbon precursor, and Co 3 O 4 is then deposited to LSAC by oxidation-precipitation and crystallization process of Co ions from Co(NO 3) 2 solution. The Co 3 O 4 particles uniformly decorate on the surface and/or the inner channels of LSAC. The optimal reflection loss (RL) value of LSAC/Co 3 O 4 -paraffin wax (PW) composite reaches −39.8 dB, and the bandwidth for RL below −10 dB and −20 dB are 10.3 and 3.0 GHz, respectively, much better than that of LSAC-PW composite for the higher magnetic loss. The addition of Co 3 O 4 particles in LSAC-PW composite significantly enhance the RL values in various thicknesses. The channels of the LSAC and decorated Co 3 O 4 can improve the abilities of multiple scattering, dipole polarization, interface polarization and magnetic loss. This composite provides a promising method to construct high performance absorbers by using biomass carbon to tune the dielectric properties of the ferromagnetic materials. [ABSTRACT FROM AUTHOR]

Abstract In this report, we systematically studied the dielectric properties of alternately doped Ba 1-x Sr x TiO 3 films with different Ba/Sr ratios. All species are polycrystalline with an ABO 3 -type structure, which exhibits growth mainly along the (110) crystal face, showing intense crystallization. Regardless of the phase of the films, either ferroelectric or paraelectric, the variation in dielectric loss is insignificant, which can be attributed to the weakening of the domain wall motion. The contribution of domain wall motion to the total losses is only approximately 6.4%, as determined by hyperbolic law calculations. In addition, a model was proposed that can well explain the pinning effect of space charge on the domain wall motion. Furthermore, the FOM value and J-V characteristics indicate that the alternately doped film still possesses good dielectric performance, even in the ferroelectric phase. [ABSTRACT FROM AUTHOR]

The domain structures and phase evolution in mixed ferroelectric (Fe): KTa 1− x Nb x O 3 (KTN) crystals were investigated. Temperature dependent Raman spectra show that Curie temperatures of KTN and Fe: KTN are far below room temperature, but the ferroelectric domain switching was still visualized by scanning probe microscopy at room temperature. These observed domains origin from the nano-regions near the grain boundaries. In addition, the intrinsic domains (triangle for KTN and straight line/stripe for Fe: KTN) could only be observed at low temperature by transmission electron microscopy. Three phase transitions in Fe: KTN crystals were found by Raman spectroscopy and dielectric testing: 175 K for Rhombohedral-to-Orthorhombic ( R – O ), 210 K for Orthorhombic-to-Tetragonal ( O – T ) and 250 K for Tetragonal-to-Cubic ( T – C ), which is consistent with the domain behavior. [ABSTRACT FROM AUTHOR]

0.5Ba(Ti 0.8 Zr 0.2 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (0.5BZT-0.5BCT), one of the most promising lead-free piezoelectric materials invented in recent years, has not been optimized for its thin film to show best electric performance. In this work, 0.5BZT-0.5BCT thin films were fabricated via a sol-gel technique, and the effects of solvent and additive on the microstructure, morphology and dielectric, ferroelectric, and piezoelectric properties were studied. Results showed that the 2-methoxyethanol (2-MOE) solvent resulted in 0.5BZT-0.5BCT thin films with much improved microstructure and morphology in comparison with thin film from absolute ethanol solvent. Furthermore, the film becomes even denser, smoother, and more homogeneous after the monomer ethylene glycol (EG) or polyethylene glycol of 400 molecular weights (PEG400) were added into the precursor with 2-MOE as solvent. Especially, addition of PEG400 into the solvent will result in the best thin film with both less macro and micro defects and high electric performance. The 0.5BZT-0.5BCT film from 2-MOE solvent with PEG400 additive shows a high dielectric constant ε up to 1756, dielectric tunability about 44%, P r around 17.2 μC/cm 2 , and E c about 39.0 kV/cm. [ABSTRACT FROM AUTHOR]

• Low-sintered Nd 2 (Zr 1−x Sn x) 3 (MoO 4) 9 ceramics were prepared successfully. • Rietveld refinement was used to obtain the lattice parameters. • Relationships between intrinsic factors and dielectric properties were investigated. • Performance of Nd 2 Zr 3 (MoO 4) 9 ceramics was improved by the doping of Sn4+. [Display omitted] In this work, Nd 2 (Zr 1- x Sn x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.1) (NZSM) ceramics were successfully obtained through conventional solid-state route. Phase analysis, microstructure, and properties were investigated scientifically by XRD, SEM, and network analyzer, respectively. XRD results revealed that all samples with different substitution amounts of Sn4+ formed the pure phase with R-3c space group. The permittivity was related to the polarizability and the bond of Zr2-O5, the bond of Nd-O2 possessed a positive influence on Q×f. The reduced octahedral distortion and increased bond energy made the temperature coefficient more stable. Infrared reflection spectrum results showed that the permittivity was mainly caused by the absorption of phonon oscillation. The optimum properties (ε r = 10.34, Q×f = 74,795 GHz, τ f = −13.55 ppm/°C) were obtained when x = 0.02 sintered at 750 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dielectric and impedance properties for different CLBO orientations were studied. [•] (001) face has the highest electromechanical coupling factor at 300-450°C. [•] (001) face has the highest dielectric constant, AC conductivity at high temperature. [•] The ions arrangement in CLBO leads to the anisotropy of electric properties. [ABSTRACT FROM AUTHOR]