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This paper reports on the successful preparation of LaPO4-x wt.% LiF (x = 0–5) ceramics using the traditional solid-state reaction method. The crystal structures, sintering behaviors, and dielectric response at microwave and terahertz frequencies were investigated. XRD results indicate that all the diffraction peaks were attributed to LaPO4, and no secondary phase was observed. Rietveld refinement was conducted to analyze the variation of the crystal structure of LaPO4-x wt.% LiF. SEM indicates that the addition of LiF significantly decreased the grain size while increasing the apparent density of the ceramics. When x = 3, the optimum microwave dielectric properties εr = 10.03, Q × f = 81,467 GHz, and τf = −43.79 ppm/°C were achieved in LaPO4-3 wt.% LiF ceramic at 750 °C. The infrared reflectance spectrum and terahertz time-domain spectroscopy were analyzed and compared with the dielectric properties measured at microwave frequency to investigate the inherent dielectric response. The findings indicate that the dielectric constant attributed to ionic displacement polarization and oxygen vacancy is an essential factor affecting dielectric loss. Moreover, it is worth noting that the LaPO4-3 wt.% LiF ceramic demonstrates excellent compatibility with silver powders, suggesting its immense potential as a dielectric material in LTCC applications. [ABSTRACT FROM AUTHOR]

A new type of microwave dielectric ceramics with low dielectric loss was fabricated through a traditional solid-phase method. X-ray diffraction and density tests showed that KSrPO 4 ceramics with a single orthorhombic phase could be synthesized and densified at 950 °C, and the crystal structure of KSrPO 4 was further confirmed by Rietveld refinement analysis. The densification temperature of KSrPO 4 was lower than 961 °C, indicating the ceramics could be used in LTCC devices. Additionally, based on the complex chemical bond theory, some internal parameters of KSrPO 4 ceramics were calculated and the effects of these parameters on the properties of KSrPO 4 were systematically analyzed for the first time. Furthermore, the composite dielectric constant and loss of KSrPO 4 ceramics were analyzed by infrared reflectance spectroscopy, and the theoretical loss and the actual loss were compared. Finally, a vector network analyzer was employed to measure the microwave dielectric properties of all samples. The results showed that KSrPO 4 sintered at 950 °C obtain the best microwave dielectric properties, including ε r = 7.85, Q·f = 34,527 GHz (at 10.43 GHz) and τ f = −14.82 ppm/°C. [ABSTRACT FROM AUTHOR]

A series of trigonal system Ce 2 Zr 3 (Mo 1- x W x O 4) 9 (CZM 1- x W x) (0.02 ≤ x ≤ 0.10) ceramics with space group R-3c were fabricated by solid-state synthesis method. The impacts of substituting W6+ for Mo6+ on the apparent morphology, structural parameters, microwave dielectric performances, and crystalline phase composition were comprehensively discussed in the CZM 1- x W x solid solutions. The X-ray diffraction and classical Rietveld refinement were performed to analysis the crystalline structure, which identified that all the as-synthesized CZM 1- x W x ceramic samples only contained a single phase without additional impurities. SEM photographs revealed that clear grain boundaries and well-densified microstructure could be acquired at the optimal temperature of 875 °C for the CZM 1- x W x ceramics. Combined with the extrinsic and intrinsic factors, the reduction of ε r was associated with porosity, ionic polarizability of primitive unit cell and average bond ionicity. The change in Q·f values could be explained by packing fraction and lattice energy of Mo-site. The variation in τ f values were governed by bond valence, bond energy and thermal expansion coefficient of Mo/W–O bond. Besides, the relationship between IR spectra and intrinsic dielectric properties were investigated. In total, the considerable and comprehensive microwave dielectric properties with ε r = 10.27, Q·f = 65,553 GHz (at 9.86 GHz), and τ f = −10.13 ppm/°C were realized at the low temperature of 875 °C for the CZM 1- x W x ceramics with x = 0.04. [ABSTRACT FROM AUTHOR]

La 2 (Zr 1- x Sn x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.10) (LZMS) materials were successfully synthesized to scientifically investigate the effects of Sn4+ addition on phase composition, microstructures, lattice vibration, and dielectric response at microwave frequency. XRD patterns indicate that all samples belong to the trigonal crystal (S.G. R-3c). The crystallite size and lattice strain were analyzed using the Willimson-Hall equation. According to the apparent density and SEM, the LZMS ceramics achieved a dense and homogeneous microstructure when sintered at 700 °C. Analysis of the microwave dielectric properties revealed that the ceramics with x = 0.06 sintered at 700 °C achieved excellent performances (Qf = 75,508 GHz, ε r = 10.18, τ f = −22.21 ppm/°C). The far-infrared reflectance spectrum shows that the theoretical permittivity of the ceramic was mainly from the absorption of phonon vibrations below 400 cm-1. Consequently, the La 2 (Zr 0.94 Sn 0.06) 3 (MoO 4) 9 ceramic has excellent microwave dielectric properties and can be used as a material for 5G communication devices. [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]

• Low-sintered Ce 2 [Zr 1−x (Zn 1/3 Ta 2/3) 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 Ce 2 Zr 3 (MoO 4) 9 ceramics was improved by the doping of (Zn 1/3 Ta 2/3)4+. [Display omitted] Ce 2 [Zr 1−x (Zn 1/3 Ta 2/3) x ] 3 (MoO 4) 9 compounds were successfully prepared and researched. Phase analysis, microstructures and properties were studied scientifically by XRD, SEM and network analyzer, respectively. Rietveld refinement of all compositions confirmed that a single phase in trigonal crystal structure with R -3 c space group was obtained. Infrared reflection spectrum results showed the permittivity was related to the absorption of phonon oscillation. SEM images revealed that the average grain size decreased with the increase of (Zn 1/3 Ta 2/3)4+. Microwave dielectric properties analysis indicated that the permittivity was related to the polarizability, Mo-O made a more significant contribution to the Q × f , and τ f was related to the octahedral distortion. The optimum properties (ε r = 10.77, Q × f = 74,682 GHz, τ f = −12.84 ppm/°C) were obtained when x = 0.04 sintered at 750 °C. [ABSTRACT FROM AUTHOR]

In this contribution, Ce 2 [(Zr 1- x (Zn 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1− x (ZS) x) (0 ≤ x ≤ 0.1) ceramics were fabricated using the solid-state reaction method, and the phase composition of the synthesized ceramics was analyzed via XRD and Rietveld refinement. The outcomes revealed that the ceramics, characterized by different x values, constituted a solitary phase with an R-3C space group, and the cell volume demonstrated a decrease with an increase in x value. The examination of the ceramics microwave dielectric characteristics using P–V−L theory reveals that the f i (Ce – O(6)) bond was found to be related to ε r , while Q × f was influenced by the average grain size and U ave. (Mo – O) , and E ave. (Mo – O) and α ave. (Mo – O) were related to the τ f value. The optimal properties were achieved at 750 °C (x = 0.02), resulting in ε r = 10.08, Q × f = 100,954 GHz, τ f = −12.46 ppm/°C. The infrared reflection spectrum analysis revealed that the primary polarization contribution was due to the dielectric response of intrinsic phonons. Additionally, the effects of three different complex ions (Zn 1/2 Sb 2/3)4+, (Zn 1/2 Ta 2/3)4+, and (Zn 1/2 Nb 2/3)4+ doping on the properties of Ce 2 Zr 3 (MoO 4) 9 ceramics were investigated using SEM, packing fraction, and chemical bond analysis. The results showed that (Zn 1/2 Sb 2/3)4+ doping was effective in improving the grain size and apparent density of Ce 2 Zr 3 (MoO 4) 9 ceramics, and the high packing fraction and U (Mo – O) were found to be the primary intrinsic factors for the optimal properties. [ABSTRACT FROM AUTHOR]

In this study, Ce 2 [Zr 1 x (Ba 1/3 Ta 2/3) x ] 3 (MoO 4) 9 (CZ 1 x T x , x = 0.01 ∼ 0.1) ceramics were synthesized via the solid-state method at temperatures ranging from 650 °C to 850 °C. XRD and Rietveld refinement analyses revealed that CZ 1 x T x ceramics exhibit a single phase with the space group R 3-c, and the cell volume increases with higher doping content. SEM results indicate that CZ 0.98 T 0.02 ceramics exhibit a highly regular and uniform grain shape. The CZ 0.98 T 0.02 ceramics displayed optimal performance at 800 °C, exhibiting ε r = 10.40, Q × f = 76,893 GHz, and τ f = 14.61 ppm/°C. Additionally, the P-V-L theory was employed to establish correlations between ceramic chemical bonds and performance attributes. The results showed that the Ce-O bond predominantly influences ε r while the Mo-O bond correlates with Q × f and τ f. Furthermore, far-IR reflection spectra unveiled ion displacement polarization as the primary mechanism in CZ 1 x T x ceramics. Finally, based on CZ 0.0.98 T 0.02 ceramics, a patch antenna applicable to the S-band was designed and fabricated, evidencing the vast potential of this ceramic in industrial applications. • The influence of (Ba1/3Ta2/3)4+ ions on Ce2Zr3(MoO4)9 ceramics was studied. • The PVL theory was used to study the chemical bond characteristics of ceramics. • The analysis of the ceramic's lattice vibrations was conducted. • A patch antenna suitable for the S-band was designed and fabricated. [ABSTRACT FROM AUTHOR]

In this article, a series of Pr 2 Zr 3 (Mo 1− x W x O 4) 9 ceramics were prepared using the solid-state reaction method and investigated in terms of phase compositions, lattice stress, lattice vibrations, and dielectric properties at microwave, terahertz, and infrared regions. X-ray diffraction (XRD) analysis revealed that all ceramics possess a trigonal structure (R-3c space group) with no discernible second-phase presence. Moreover, the ceramics exhibit oriented growth along the (0,0,18) crystal plane. The densification of all ceramics occurred within the range of 800–825 °C. Raman spectroscopy exhibited a minor blue shift in the predominant peak as the x value increased. The complex permittivity (ε′ and ε″) were evaluated using both infrared reflectance spectrum and terahertz time-domain (THz-TD) spectroscopy. Interestingly, the THz-TD spectral data exhibited a closer agreement with the measured values, which was attributed to a significant relaxation polarization mechanism. Specifically, the peaks below 400 cm−1 contributed significantly to the dielectric parameters, accounting for 88.4% and 95.7% of ε′ and ε″, respectively. As a result of these findings, it is suggested that Pr 2 Zr 3 (Mo 0.94 W 0.06 O 4) 9 (ε r = 9.82, Qf = 81,892 GHz, τ f = −17.90 ppm/°C) ceramics synthesized at 825 °C hold promise as potential materials for high-frequency communication circuits. [ABSTRACT FROM AUTHOR]

Novel Ce 2 (MoO 4) 2 (Mo 2 O 7) (CMO) ceramics were prepared by a conventional solid-state method, and the microwave dielectric properties were investigated. X-ray diffraction results illustrated that pure Ce 2 (MoO 4) 2 (Mo 2 O 7) structure formed upon sintering at 600 °C-725 °C. [CeO 7 ], [CeO 8 ], [MoO 4 ], and [MoO 6 ] polyhedra were connected to form a three-dimensional structure of CMO ceramics. Analysis based on chemical bond theory indicated that the Mo–O bond critically affected the ceramics' performance. Furthermore, infrared-reflectivity spectra analysis revealed that the primary polarisation contribution was from ionic polarisation. Notably, the optimum microwave dielectric properties of ε r = 10.69, Q·f = 49,440 GHz (@ 9.29 GHz), and τ f = −30.4 ppm/°C were obtained in CMO ceramics sintered at 700 °C. [ABSTRACT FROM AUTHOR]

A series of Ce 2 (Zr 1− x Sn x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.1) (CZ 1− x S x M) ceramics were synthesized to investigate the effect of Sn4+ doping on the crystal structure, chemical bond parameters, and dielectric properties of Ce 2 Zr 3 (MoO 4) 9 ceramics. X-ray diffraction patterns illustrated the formation of the single-phase trigonal system solid solution in all samples. Rietveld refinement result showed that the lattice volume decreased linearly, which can be explained by the fact that the effective radius of Sn ion is smaller than that of Zr ion. As the Sn content increased, scanning electron microscope images showed that the CZ 1− x S x M ceramics transformed from bar-like grains to disk-like grains and the grain size declined gradually. The structure–property correlation was estimated by using P–V-L theory; the descending ε r was mainly consistent with the reduced polarizability and total bond ionicity. The Q × f was associated with the lattice energy of the Ce–O1 bond. The change of τ f value was mainly attributed to the bond energy (E Mo1 – O1 and E Mo1 – O4) and the coefficients of thermal expansion (α Mo1 – O1 and α Mo1 – O4). Infrared analysis indicated that the dielectric properties of the CZ 1− x S x M ceramics were primarily ascribed to the absorption of phonon oscillation. Notably, when x = 0.08, outstanding microwave dielectric properties could be achieved, namely, ε r = 10.22, Q × f = 72,390 GHz, τ f = −7.54 ppm/°C. [ABSTRACT FROM AUTHOR]

A series of Ce 2 (Zr 1− x B x) 3 (MoO 4) 9 ceramics, where B Cd 1/3 Nb 2/3 , Cd 1/3 Ta 2/3 (abbreviated as CZ 1− x N x , CZ 1− x T x), were synthesized using the classical solid-state reaction method. This study focused on the intrinsic mechanisms affected by doping in terms of chemical bond parameters, polarizability, lattice parameters, and bond valence. X-ray diffraction (XRD) results showed that Cd/Nb and Cd/Ta were solidly dissolved into the matrix lattice, which crystallized in a pure trigonal structure (Space group of R -3c, No. 167). According to the Phillips-van Vechten-Levine (P–V-L) theory, the chemical bond features have been parameterized for exploring the relationships between crystal structure and property. Interestingly, the findings indicated that the dielectric parameters varied closely with the chemical bond features of Zr1–O4. Far-infrared reflectivity (FIR) spectrum and terahertz time-domain (THz-TD) were used to obtain information on lattice vibration. The results showed that the complex permittivity extrapolated from THz-TD was closer to the measured value (at microwave) than the former. The relaxation polarization mechanism may be a key intrinsic factor affecting dielectric loss. Additionally, the bond valence results showed a linear relationship between Zr1–O4 and τ f. CZ 1− x N x and CZ 1− x T x exhibited Qf values that were 2.86 and 5.46 times greater than the matrix, respectively, with low permittivity (ε r , roughly 10) suitable for high-frequency communication materials. Notably, CZ 0.94 T 0.06 ceramic achieved excellent performance with Qf = 103,974 GHz, ε r = 10.63, and τ f = −17.68 ppm/°C at 725 °C. [ABSTRACT FROM AUTHOR]

Molybdenum oxide-based ceramics have attracted intense interest due to ultra-low sintering temperatures. However, low quality factors (Q × f) hinder their practical applications. Although Q × f can be improved by ions doping, the sintering temperature is greatly increased. Accordingly, it is still a challenge to obtain high Q × f ceramics sintered at ultra-low temperatures (<660 °C). Herein, (Bi 0.5 Ta 0.5)4+ ions are utilized to tackle this issue in the Ce 2 Zr 3 (MoO 4) 9 ceramic as a prototype. Density and scanning electron microscope (SEM) results uncover good sintering states, and X-ray diffraction (XRD) results reveal the formation of solid solutions. Interestingly, the Ce-O bonds exhibit a dominant contribution to the bond ionicity (f i), while Mo-O bonds play an important role in the lattice energy (U), the bond energy (E) and the thermal expansion coefficient (α). The remarkable increase of Q × f can be interpreted by the enhancement of the packing fraction and the mean U of Mo-O bonds. Moreover, the variations of the dielectric constant (ε r) and the temperature coefficient of the resonance frequency (τ f) can be explained by the variations of the intrinsic parameters. More interestingly, a negative correlation between Q × f and τ f is first found. Typically, the CZ 0.98 B 0.02 ceramic sintered at 650 °C exhibits optimum microwave dielectric properties: ε r = 9.92, Q × f = 110,670 GHz, and τ f = −19.20 ppm °C−1. Notably, Q × f of the Ce 2 Zr 2.94 Bi 0.03 Ta 0.03 Mo 9 O 36 (CZ 0.98 B 0.02) ceramic is about 6 times larger than that of the matrix while retaining a low sintering temperature of 650 °C and a low ε r of 9.92, making it a promising candidate for ultra-low temperature cofired ceramics (ULTCC) applications. [ABSTRACT FROM AUTHOR]

A series of Ce 2 [Zr 1- x (A) x ] 3 (MoO 4) 9 (A = Sr 1/3 Ta 2/3 , Sr 1/3 Sb 2/3 ; x = 0.02, 0.04, 0.06, 0.08 and 0.10) (abbreviated as CZ 1- x T x and CZ 1- x S x) microwave dielectric ceramics were studied systematically with respect to microstructures, sintering behaviors, crystal structures, microwave dielectric properties and infrared vibrational modes. Density measurements and scanning electron microscopy (SEM) reveal the dense and homogeneous microstructures. X-ray diffraction (XRD) results confirm the formation of solid solutions belonging to the hexagonal system with a R 3 ‾ c space group, and the lattice volume increases with raising the doping content. Furthermore, the complex chemical bond theory was used to calculate the intrinsic bond parameters, and the correlations between the microwave dielectric properties and intrinsic bond parameters were established. Finally, far infrared (FIR) spectra reveal that the main polarization contribution stems from the absorptions of the phonon oscillations in these two groups of ceramics. Typically, the optimum microwave dielectric properties are achieved for CZ 0.9 T 0.1 and CZ 0.94 S 0.06 ceramics with ε r = 10.24, Q × f = 92,009 GHz (at 9.70 GHz), τ f = −8.84 ppm °C−1 and ε r = 10.40, Q × f = 82,696 GHz (at 9.69 GHz) and τ f = −8.04 ppm °C−1, respectively. Interestingly, the CZ 0.9 T 0.1 ceramic exhibits the maximum Q × f value in the ion doped Ce 2 Zr 3 (MoO 4) 9 ceramics while retaining a good τ f = −8.84 ppm °C−1. [ABSTRACT FROM AUTHOR]

Ce 2 [Zr 1- x M x ] 3 (MoO 4) 9 (M = Mn 1/3 Nb 2/3 , Mn 1/3 Ta 2/3; x = 0.02, 0.04, 0.06, 0.08 and 0.10) (abbreviated as CZ 1- x N x and CZ 1- x T x) ceramics were prepared through the solid-state reaction method. Effects of (Mn 1/3 Nb 2/3)4+ and (Mn 1/3 Ta 2/3)4+ ions on the sintering characteristics, crystal structures, microwave dielectric properties and infrared vibrational modes were studied in detail. X-ray diffraction (XRD) results reveal the formation of solid solutions for all components. Based on the chemical bond theory and Rietveld refinement, intrinsic structure parameters including the polarizability (P), the packing fraction (P.F.) and the octahedral distortion (Δ octa.), and bond parameters including the lattice energy (U), bond energy (E) and thermal expansion coefficient (α) were calculated. Interestingly, the Ce–O bond plays a major role in the bond ionicity (f i), while Mo–O bond dominates the contributions in the lattice energy (U), bond energy (E) and thermal expansion coefficient (α). In addition, these parameters are used to explain the variations of the microwave dielectric properties of ceramics either changing the doping contents or replacing different ions at x = 0.06. Furthermore, far infrared (FIR) spectra uncover that the phonon modes provide the major polarization contribution of 68.59% in the CZ 0.9 T 0.1 ceramic, implying that the main contribution to ε r stems from the ionic polarization instead of the electronic polarization. Typically, the optimum microwave dielectric properties are achieved for the CZ 0.9 N 0.1 and CZ 0.9 T 0.1 ceramics with ε r = 10.76, Q × f = 85,893 GHz (at 9.52 GHz), τ f = −14.83 ppm °C−1 and ε r = 10.72, Q × f = 87,355 GHz (at 9.81 GHz) and τ f = −8.68 ppm °C−1, respectively. Notably, the CZ 0.9 T 0.1 ceramic has a markedly increased Q × f while maintaining a good τ f = −8.68 ppm °C−1 and a low sintering temperature of 700 °C. [ABSTRACT FROM AUTHOR]

In this research, Cr/Sb was co-doped in Ce 2 Zr 3 (MoO 4) 9 ceramic to optimize the microwave dielectrics and explore the intrinsic mechanism. All ceramics were synthesized using the traditional ceramic method to investigate the effects of Cr/Sb on the microstructure, chemical bond characteristics, phonon vibration spectra, and dielectric response at microwave and terahertz frequencies. X-ray diffraction analysis identified that all samples crystallized in a trigonal system, and no additional peaks observed. The dense ceramic was obtained at 875 °C based on the observed sintering behaviors. The co-addition of Cr/Sb significantly reduced the dielectric loss in the matrix. Therefore, dielectric parameters were discussed in terms of intrinsic factors. The findings of chemical bond indicate that Zr(Cr/Sb)–O bonds possess a close relationship with microwave dielectric properties, and Cr/Sb is occupied preferentially on the Zr(1) sites. Infrared spectrum analysis identified that phonon vibration lower than 400 cm−1 contribute 72.1% to the polarization. In our comparison between the infrared spectrum and terahertz time-domain (THz-TD) spectrum, we found that the permittivity extracted by the latter is closer to the observed value. Consequently, the outstanding parameters of ε r = 10.53, Qf = 72,656 GHz, τ f = −16.77 ppm/°C were obtained in the Ce 2 [Zr 0.98 (Cr 0.5 Sb 0.5) 0.02 ] 3 (MoO 4) 9 ceramic. [ABSTRACT FROM AUTHOR]

In this study, Ce 2 [Zr 1− x (Cr 0.5 Ta 0.5) x ] 3 (MoO 4) 9 (x = 0.02–0.10) ceramics were synthesized using the solid-state reaction technique, and the crystalline parameters, sintering behaviors, chemical bond characteristics, infrared reflection spectrum, and dielectric response at microwave and terahertz frequency were examined. X-ray diffraction results demonstrated the crystallization of all ceramics in the trigonal structure (R-3c space group), and additional peaks were not detected. The densification point of ceramic was 875 °C. The addition of (Cr 0.5 Ta 0.5)4+ significantly reduced the dielectric loss in the host ceramic. For Ce 2 [Zr 0.96 (Cr 0.5 Ta 0.5) 0.04 ] 3 (MoO 4) 9 , outstanding microwave properties of ε r = 10.66, Qf = 79,436 GHz, and τ f = −19.07 ppm/°C were obtained at 875 °C. The chemical bond characteristics were also parameterized to explore the relationship between Zr(CrTa)–O and microwave properties. Infrared spectral results further indicate that phonon vibrations lower than 400 cm−1 contribute to 80% of the polarization. In our comparison between the infrared spectrum and terahertz time-domain spectrum, we found that the permittivity extracted by the latter is closer to the observed value. [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]

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]

• Li 2 Mg 4 Zr 1–x (Mg 1/3 Sb 2/3) x O 7 (x = 0.10–0.25) microwave dielectric ceramics were prepared. • Rietveld refinement was used to obtain the lattice parameters. • Relationships among intrinsic factors and dielectric properties were investigated. • Li 2 Mg 4 Zr 0.8 (Mg 1/3 Sb 2/3) 0.2 O 7 materials with ɛ r = 12.29, Q×f = 153,140 GHz, and τ f = -17.7 ppm/°C were obtained. ga1 In this work, a series Li 2 Mg 4 Zr 1−x (Mg 1/3 Sb 2/3) x O 7 (x = 0.10–0.25) ceramics were synthesized using the classical solid-state reaction method. The effects of (Mg 1/3 Sb 2/3)4+ in the microstructures, sintering behaviors, and microwave dielectric properties of Li 2 Mg 4 Zr 1−x (Mg 1/3 Sb 2/3) x O 7 ceramics were investigated systematically. XRD analyses indicate that all samples were the rock-salt structure with the Fm -3 m space group, the crystalline parameters were obtained using the Rietveld refinement. Based on the complex chemical bond theory, the effects of inherent features (e.g. bond ionicity, bond energy, and lattice energy) on the dielectric performance of Li 2 Mg 4 Zr 1−x (Mg 1/3 Sb 2/3) x O 7 ceramics were analyzed in details. By adding proper content of (Mg 1/3 Sb 2/3)4+, the optimal dielectric performance of ɛ r = 12.29, Q × f = 153,140 GHz, and τ f = −17.7 ppm/°C were obtained in the Li 2 Mg 4 Zr 0.8 (Mg 1/3 Sb 2/3) 0.2 O 7 materials at 1600 °C for 4 h. The quality factor is more than 100 THz, which indicates that the Li 2 Mg 4 Zr 0.8 (Mg 1/3 Sb 2/3) 0.2 O 7 ceramic is a good candidate for the highly selective filters or microwave resonators. [ABSTRACT FROM AUTHOR]

The single-phase of Ce 2 [Zr 1- x (Ba 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (x = 0.01 ∼ 0.10) (CZBS x M) ceramics were synthesized by the classic solid-state route successfully. The influence of (Ba 1/3 Sb 2/3)4+ replacement for Zr4+ on the lattice parameters, microstructure, chemical bonds and dielectric properties were discussed comprehensively. The X-ray diffraction (XRD) indicated that the CZBS x M ceramics are trigonal-type crystal structure with R-3c space group. The lattice parameters of CZBS x M ceramics were obtained via the Rietveld refinement method. The theory of complex crystals chemical bonds (P-V-L theory) was carried out to study the connections between the chemical bond and dielectric properties. The excellent dielectric properties (ɛ r = 10.71, Q×f = 91,798 GHz and τ f = −15.18 ppm/℃) were obtained at 700 ℃ in CZBS 0.02 M ceramic. [Display omitted] • The effects of (Ba 1/3 Sb 2/3)4+ substitution for Zr4+ on dielectric properties in Ce 2 Zr 3 (MoO 4) 9 was discussed by P-V-L theory. • The Q × f value of Ce 2 Zr 3 (MoO 4) 9 ceramic was increased by more than 3.5 times via doping of (Ba 1/3 Sb 2/3)4+ ions. • The optimum microwave dielectric properties (ɛr = 10.71, Q×f = 91,798 GHz, τf = −15.18 ppm/℃) were obtained at x = 0.02. [ABSTRACT FROM AUTHOR]

Ceramics with composition of Pr 2 (Zr 1−x Ti x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.10) were fabricated by classic solid-phase method. X-ray diffractometer (XRD), Scanning electron microscope (SEM), Raman spectra, FT-IR spectrometer and Agilent vector network analyzer were used to investigate the composition of phase, microscopy, lattice vibration, internal dielectric responding and dielectric properties, respectively. XRD indicates the Pr 2 (Zr 1−x Ti x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.10) ceramics own trigonal-type crystal structure and R-3c space group and the SEM patterns confirms the optimal sintering temperature is 800 °C. Simultaneously, the ceramic reached the optimal microwave dielectric properties with ε r = 10.8, Q×f = 81,539 GHz and τ f = −14.2 ppm/°C at 800 °C for x = 0.10. By means of the theory of complex crystals chemical bonds (P-V-L theory), the connections with crystal structure and microwave dielectric properties were deeply discussed. Due to the relatively low fired temperature and superior dielectric properties, there is an expect for Pr 2 (Zr 0.90 Ti 0.10) 3 (MoO 4) 9 ceramic to apply in low temperature cofired ceramic (LTCC). [Display omitted] • Rietveld refinement was used to obtain the cell parameters. • The effects of substitution of Zr4+ by Ti4+ on Pr 2 Zr 3 (MoO 4) 9 ceramics was explored based on the P-V-L theory. • Q·f value has been improved by more than 130% in Pr 2 (Zr 0.90 Ti 0.10) 3 (MoO 4) 9 ceramics. • Optimum microwave dielectric properties (ε r = 10.8, Q×f = 81,539 GHz and τ f = −14.2 ppm/°C) were obtained at 800 °C. [ABSTRACT FROM AUTHOR]

• The sintering temperature of CZ 1− x (MS) x M ceramic was below 900 °C. • Effect of bond characteristics on microwave dielectric properties was discussed. • Infrared reflectivity spectrum was adapted to investigate intrinsic properties. [Display omitted] Ce 2 [Zr 1− x (Mn 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (x = 0.1–1.0) ceramics were prepared by a conventional solid-state method. (Mn 1/3 Sb 2/3)4+ ions occupied the Zr-site, and Ce 2 [Zr 1− x (Mn 1/3 Sb 2/3) x ] 3 (MoO 4) 9 solid solution was obtained. With x value increased, the ε r decreased from 10.47 (x = 0.02) to 10.10 (x = 0.10), which was affected by bond ionicity of Zr/(Mn 1/3 Sb 2/3)1 O4 bond. The Q·f value first increased and then decreased, which was controlled by varying packing fraction, relative density, and lattice energy (Ce O bond). The thermal expansion coefficient and bond energy of Mo O bond were associated with τ f value. Besides, infrared reflection spectrum suggested that the properties were primarily derived from the absorption of phonon in the infrared range. Outstanding microwave dielectric properties of Ce 2 [Zr 0.92 (Mn 1/3 Sb 2/3) 0.08 ] 3 (MoO 4) 9 ceramics were obtained when sintered at 700 °C: ε r = 10.29, Q·f = 91,981 GHz and τ f = −9.81 ppm/°C. [ABSTRACT FROM AUTHOR]

Ce 2 Zr 3 (MoO 4) 9 (CZM) ceramics were prepared successfully through the reaction-sintering (RS) method and a single phase was detected in X-ray diffraction patterns. The microstructures of ceramics were observed by a scanning electron microscopy. Based on the results of Rietveld refinement, the influence of chemical bonds parameters on microwave dielectric properties were analyzed by complex chemical bond theory. The lattice vibrational characteristics were investigated by far-infrared reflection spectroscopy. The promising dielectric properties of CZM ceramics were ε r = 10.1, Q×f = 69,705 GHz and τ f = −6.34 ppm/°C, sintered at 850 °C. [Display omitted] • Ce 2 Zr 3 (MoO 4) 9 ceramics were prepared successfully through the reaction-sintering (RS) method. • Microwave dielectric properties were analyzed deeply by complex chemical bond theory and far-infrared reflection spectroscopy. • Effects of the distortion of oxygen octahedral on temperature coefficient of resonant frequency were discussed. [ABSTRACT FROM AUTHOR]