Complex Chemical Bond Theory Research Articles

Low‐dielectric‐loss ZnZrNb2O8 ceramics combined with H3BO3 for low‐temperature co‐fired ceramics applications

AbstractH3BO3 was used as the sintering additive to enable Zn0.997Cu0.003ZrNb2O8 ceramics to accomplish low‐temperature sintering and outstanding microwave dielectric performances. Composite ceramics were created using typical solid‐state processes. The effects of added H3BO3 on the sintering behavior, microstructural characteristics, vibrational properties, and microwave dielectric performances of Zn0.997Cu0.003ZrNb2O8 + x wt% H3BO3 (2 x 8) ceramics have been systematically investigated by means of X‐ray diffraction, Raman scattering spectroscopy, scanning electron microscopy, and complex chemical bond theory. The results of relative density and microscopic morphology demonstrated that the application of an adequate quantity of H3BO3 additive can significantly enhance sintering properties. The doped H3BO3 alters the inter‐ionic interactions so that the structural features become intrinsic to the microwave dielectric performances. The particularly satisfactory microwave dielectric performances ( = 10.61, = 33 980 GHz, and = ‐45.10 ppm/°C) were detected in x = 6 ceramic specimens sintered at 950°C, which would make it promising for use in modern low temperature co‐fired ceramics technology.

Structure, bond characteristics, and microwave dielectric properties of Ba3La(PO4)3 ceramic

The single-phase, cubic-structured Ba3La(PO4)3 ceramics were synthesized using the traditional solid-state reaction method. The ceramic sintered at 1375 °C exhibited a relative density of 95.4 %, indicative of a dense microstructure and excellent sintering characteristics. Furthermore, they displayed remarkable microwave dielectric properties: εr = 9.54, Q × f = 32820 GHz, and τf = −43.1 ppm/°C. In addition, the relative density is positively correlated with εr and Q × f of ceramics. According to the complex chemical bond theory, the ionicity of the Ba/La–O bond has a more significant impact on the εr, while the lattice energy and bond energy of the P–O bond respectively dominate the Q × f and τf values. Moreover, the results from Raman spectroscopy indicate that several prominent Raman bands are associated with the vibration of the P–O bond. These findings suggest that Ba3La(PO4)3 ceramics hold promise for applications in high-frequency microwave communication.

Crystal structure, Raman spectra, and microwave dielectric performances of TiW-substituted magnesium niobite ceramics

The effect of TiW substitution on the microwave dielectric performances of MgNb2O6 ceramics prepared via solid-state reaction has been investigated using Raman scattering spectroscopy, microscopic morphology analysis, and complex chemical bond theory. The dielectric permittivity is mainly affected by porosity, molecular polarizability and crystal vibrations. The Q×f value is mainly determined by the bond covalency of the Nb–O bond and the FWHM value of the Raman spectrum. In addition, τf value is mainly affected by the bond valence of the Nb–O bond. This research demonstrates that a moderate amount of (TiW)5+ not only reduces the sintering temperature (from 1460 °C to 1340 °C) and lowers the dielectric loss, but also improves the temperature stability. The composition (x = 0.01) exhibits excellent properties: εr = 20.67, Q×f = 117,660 GHz, and τf = −45.73 ppm/°C, providing a promising candidate for 5 G electronic devices.

Microwave dielectric properties and sintering behavior of a novel low-cost lightweight,middle-εr Na2Ti6O13 ceramics

In order to develop novel lightweight low-cost microwave dielectric ceramics (MDCs), middle-εr Na2Ti6O13 ceramics were prepared by a traditional solid-state reaction method and the sintering behavior and microwave dielectric properties ((MDPs) were investigated. The detailed structural parameters of the Na2Ti6O13 ceramics were obtained by X-ray diffraction and Rietveld refinement, and the chemical bond characteristics of the structures were further studied using Raman spectroscopy. The relative density of the ceramics and scanning electron microscopy (SEM) images show that density and porosity are important factors affecting the dielectric properties of the samples. Based on the acquired Raman spectra and complex chemical bond theory (P–V–L theory), the chemical bond properties were calculated and analyzed, and the effects of intrinsic factors on the MDPs were investigated. The MDPs of Na2Ti6O13 ceramic sintered at 1025 °C were as follows: εr = 34.3, Q×f = 33660 GHz, and τf = 40.3 ppm/°C.

Optimized crystal structure and microwave dielectric properties of BaZnSi3O8‐based ceramics

AbstractIn this study, we synthesized BaZnSi3O8‐based compounds with monoclinic structures (P21/a) using a solid‐state method. The crystal structure, phase composition, and microwave dielectric properties of BaZnSi3O8‐based ceramics were systematically investigated systematically. X‐ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images proved that the maximum solubility of BaZn1‐xMgxSi3O8 ranged between 0.3 and 0.4. Rietveld refinement and Phillips–Van Vechten–Levine complex chemical bond theory were used to illustrate the relationship between the microwave dielectric performance and lattice parameters. To further improve the properties, we substituted Ba2+ with Sr2+ in BaZn0.8Mg0.2Si3O8. Ba1‐ySryZn0.8Mg0.2Si3O8 remained in a single‐phase as y increased from 0 to 1.0. We achieved thermal stability of the resonance frequency of the BaZnSi3O8‐based ceramics by adjusting TiO2 to form composite ceramics. After sintering at 1020°C for 5 h, excellent microwave dielectric properties with εr = 7.44, Q×f = 57,400 GHz, and τf = − 0.2 ppm/°C were realized in the SrZn0.8Mg0.2Si3O8+8 wt %TiO2 system.

Phase Structure, Bond Features, and Microwave Dielectric Characteristics of Ruddlesden-Popper Type Sr2TiO4 Ceramics.

This work studied the phase constitution, bond characteristics, and microwave dielectric performances of Sr2TiO4 ceramics. Based on XRD and Rietveld refinement analysis, pure tetragonal Ruddlesden-Popper type Sr2TiO4 ceramic is synthesized at 1425~1525 °C. Meanwhile, the microstructure is dense and without porosity, indicating its high sinterability and densification. Great microwave dielectric performances can be obtained, namely an εr value of 39.41, and a Q × f value of 93,120 GHz, when sintered at 1475 °C. Under ideal sintering conditions, the extrinsic factors are minimized and can be ignored. Thus, the intrinsic factors are considered crucial in determining microwave dielectric performances. Based on the P-V-L complex chemical bond theory calculation, the largest bond ionicity, and proportions to the bond susceptibility from Sr-O bonds suggest that Sr-O bonds mainly determine the dielectric polarizability. However, the Ti-O bonds show lattice energy about three times larger than Sr-O bonds, emphasizing that the structural stability of Sr2TiO4 ceramics is dominated by Ti-O bonds, and the Ti-O bonds are vital in determining the intrinsic dielectric loss. The thermal expansion coefficient value of the Sr2TiO4 structure is also mainly decided by Ti-O bonds.

Investigation on the bond characteristics and microwave dielectric properties of rock salt-structured Li2Mg0.5nTiO3+0.5n (n = 1–8) ceramics based on the complex chemical bond theory

Cubic rock salt structured ceramics are of great interest due to their outstanding microwave dielectric properties. Complex chemical bond theory and polarization theory combined with XRD refinement as well as XPS were employed to reveal the mechanisms of the compositional effect on the microwave dielectric properties of Li2Mg0.5nTiO3+0.5n ceramics with a rock salt structure. It was demonstrated that when n = 1, the microwave dielectric properties exhibit a biphasic structure. However, as n increased to 2 and higher levels, the specimens were consisted of a single cubic rock salt phase. εr of single-phased samples decreased with an increase in the n value, which was due to the decreases in both the bond ionicity and polarizability of unit cell. Meanwhile, as lattice energy increased, the formation of oxygen vacancies was effectively suppressed, and anharmonic lattice vibrations were weakened, leading to an increase in Q×f. Moreover, τf showed a negative shift due to an increase in the aL,ave of the chemical bond and an decrease in the bond energy. The optimal microwave dielectric properties of εr= 17.3, Q×f= 81,000 GHz, and τf = −7.7 ppm/℃ were achieved in the component with n = 1 when sintered at 1350 °C for 4 h.

A novel Li3Mg3NbO7 microwave dielectric ceramic with ultra-low loss

Novel ultra-low-loss Li3Mg3NbO7 ceramics were synthesized using solid-state reaction method. The microstructure, bond characteristics, and microwave dielectric properties (MDPs) of the Li3Mg3NbO7 ceramics were explored. Furthermore, the Li3Mg3NbO7 ceramics crystallized in the orthorhombic rock-salt structure and the optimized density (97.7%) was obtained at 1200 °C. Utilizing complex chemical bond theory (P–V-L theory) and Raman spectra, the connection between structure and properties was constructed. εr value was mainly affected by the ρrel and average ionic polarization. The UNb–O and packing fraction were the key internal factors influencing the Q × f value. The τf was intimately relevant to Nb–O bond and τε. Notably, the Li3Mg3NbO7 ceramics sintered at 1200 °C exhibited excellent MDPs (εr = 14.7, Q × f = 121,047 GHz, τf = −24.8 ppm/°C), offering enormous prospects for 5G/6G communication applications.

Crystal structure, bond characteristics and microwave dielectric properties of Ce2[Zr1-x(Sr1/3B2/3)x]3(MoO4)9 (B = Ta, Sb) solid solutions

A series of Ce2[Zr1-x(A)x]3(MoO4)9 (A = Sr1/3Ta2/3, Sr1/3Sb2/3; x = 0.02, 0.04, 0.06, 0.08 and 0.10) (abbreviated as CZ1-xTx and CZ1-xSx) 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 R3‾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 CZ0.9T0.1 and CZ0.94S0.06 ceramics with εr = 10.24, Q × f = 92,009 GHz (at 9.70 GHz), τf = −8.84 ppm °C−1 and εr = 10.40, Q × f = 82,696 GHz (at 9.69 GHz) and τf = −8.04 ppm °C−1, respectively. Interestingly, the CZ0.9T0.1 ceramic exhibits the maximum Q × f value in the ion doped Ce2Zr3(MoO4)9 ceramics while retaining a good τf = −8.84 ppm °C−1.

Crystal Structure, Chemical Bond, and Microwave Dielectric Properties of Ba1-xSrx(Zn1/3Nb2/3)O3 Solid Solution Ceramics.

Ba1-xSrx(Zn1/3Nb2/3)O3 (BSZN) perovskite ceramics are prepared using the traditional solid-state reaction method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to analyze the phase composition, crystal structure, and chemical states of BSZN ceramics, respectively. In addition, the dielectric polarizability, octahedral distortion, complex chemical bond theory, and PVL theory were investigated in detail. Systematic research showed that Sr2+ addition could considerably optimize the microwave dielectric properties of BSZN ceramics. The change in τf value in the negative direction was attributed to oxygen octahedral distortion and bond energy (Eb), and the optimal value of 1.26 ppm/°C was obtained at x = 0.2. The ionic polarizability and density played a decisive role in the dielectric constant, achieving a maximum of 45.25 for the sample with x = 0.2. The full width at half-maximum (FWHM) and lattice energy (Ub) jointly contributed to improving the Q × f value, and a higher Q × f value corresponded to a smaller FWHM value and a larger Ub value. Finally, excellent microwave dielectric properties (εr = 45.25, Q × f = 72,704 GHz, and τf = 1.26 ppm/°C) were obtained for Ba0.8Sr0.2(Zn1/3Nb2/3)O3 ceramics sintered at 1500 °C for 4 h.

A new rare-earth orthovanadate microwave dielectric ceramic: ErVO4

A new microwave dielectric ceramic ErVO4 with a zircon structure was prepared by solid-state reaction method. The structure of ErVO4 was confirmed by X-ray diffraction and TEM diffraction, and no second phase was generated in the ceramic. At different sintering temperatures, slight changes in the lattice parameters affected microwave dielectric properties of the ErVO4 ceramic. Relative density, packing fractions, etc. Were investigated to analyze the variation of dielectric properties. Further the complex chemical bond theory revealed that the dielectric constant had a similar changing trend to the ionicity of bond, while the lattice energy had a positive impact on the quality factor. ErVO4 ceramic sintered at 1150 °C had the microwave dielectric properties of εr = 12.03, Q × f = 25,549 GHz, and τf = −52.89 ppm/°C.

ZnZr1−xHfxNb2O8-yTiO2-ZnZr1−xHfxNb2O8 (0.000 [formula omitted] x [formula omitted] 0.030, 0.01 [formula omitted] y [formula omitted] 0.06): An high-Q and temperature-stable microwave dielectric ceramic through laminated co-firing technique

In order to better fulfill the requirements high-performance dielectric devices for low insertion loss, compact size, and excellent temperature stability, we propose a strategy to maximize the comprehensive regulation of microwave dielectric properties. Since TiO2 has a relatively large and positive τf value, direct addition of TiO2 has often been utilized to modify the negative τf value in previous studies. In this paper, TiO2 and the laminated co-firing technique are applied to monoclinic wolframite structural ceramics. Tri-layer architectural ZnZr1−xHfxNb2O8-yTiO2-ZnZr1−xHfxNb2O8 (0.000 ≤ x ≤ 0.030, 0.01 ≤ y ≤ 0.06) ceramics were synthesized by the laminated co-firing technique. Firstly, Hf4+ ions substituted for Zr4+ ions to significantly enhance the Q×f value of ZnZrNb2O8 system. The modulation effect of Hf4+ on the crystal structure and the influence on the dielectric constant (εr), Q×f, and τf values were reasonably demonstrated by combining several characterization approaches with complex chemical bond theory. Compared with pure ZnZrNb2O8, the ZnZr0.990Hf0.010Nb2O8 ceramic achieved a nearly 65% increase in the Q×f value without excessive deterioration of other dielectric parameters. The laminated co-firing technique was then used to further modulate its εr and τf values. Notably, the ZnZr0.990Hf0.010Nb2O8-0.05TiO2-ZnZr0.990Hf0.010Nb2O8 tri-layer architectural ceramic achieved prominent comprehensive microwave dielectric characteristics: εr = 34.34, Q×f = 53,860 GHz, and τf = + 2.29 ppm/°C, making the tri-layer architecture ceramics attractive for usage in modern microwave communications.

Structure, microwave dielectric properties and bond characteristics of Mg2Ti1-x(Al1/2Ta1/2)xO4 ceramics

The microwave dielectric ceramics Mg2Ti1-x(Al1/2Ta1/2)xO4 (x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) are synthesized via solid-state reaction. The formation of pure spinel structural phase is confirmed by XRD refinement patterns. The intrinsic dielectric characteristics of Mg2Ti1-x(Al1/2Ta1/2)xO4 ceramics are researched by complex chemical bond theory (P–V–L theory) and infrared reflectivity spectra. The interaction of extrinsic (relative density) and intrinsic (dielectric polarizability) factors cause a change in εr. The lattice energy determines the variation of the Q × f. Both the τf and the total bond valence show a same changing trend. The improved microwave dielectric properties were obtained in Mg2Ti0.8(Al1/2Ta1/2)0.2O4 (εr = 14.2, Q × f = 186,060 GHz, τf = −39.27 ppm/◦C) when sintered at 1390 °C for 4 h.

Li+ enrichment to improve the microwave dielectric properties of Li2ZnTi3O8 ceramics and the relationship between structure and properties

Herein, Li+-enriched Li(1+x)2ZnTi3O8 ceramics are prepared via the solid-phase methods. As x increases, the unit cell volume gradually increases, while the grain size initially increases and then decreases gradually. The Li(1+0.06)2ZnTi3O8 ceramics exhibit the best dielectric properties: εr = 25.92, Q × f = 109534 GHz (@7.37 GHz, which is a 48 % increase compared with the stoichiometric counterpart.), and τf = −8.21 ppm/°C. The complex chemical bond theory and Raman spectroscopy reveal that Ti-O bonds have a significant effect on the dielectric properties. An optimal Li+ enrichment leads to an overall reduction in the distortion of the Li/ZnO4 tetrahedra, resulting in a reduction in τf. First-principles calculations demonstrate that a suitable excess of Li+ leads to an increase in the band-gap as well as an enhanced electron cloud density in the internal space of the Li1/ZnO4 tetrahedra, thereby increasing the Q × f. In summary, Li+-enriched Li(1+0.06)2ZnTi3O8 ceramics are promising for a wide array of applications in microwave communications.

Crystal structure and microwave dielectric characteristics of ixiolite ceramics with molybdenum ion modification and tri-layered structure

The ZnTi1−xMoxNb2O8 (0.000 ≤ x ≤ 0.060) microwave dielectric ceramics were prepared through traditional solid-state reaction. Mo4+ substitution for Ti4+ can markedly improve the microwave dielectric characteristics of ZnTiNb2O8 system. In the microstructures investigation, a suitable degree of Mo4+ substitution was shown to be useful for creating uniform grain size and minimizing dielectric loss. Raman spectroscopy and complex chemical bond theory analyses demonstrate that the bond ionicity of NbO bond is the intrinsic component influencing the εr value. The lattice energy of NbO bond, bond valence of Cation-O bond, and the FWHM of Raman spectra were the primary determinants of Q×f value. The τf value is mostly determined by variations in NbO bond energy and the bond valence of Cation-O bond. When x = 0.010, ZnTi0.990Mo0.010Nb2O8 ceramics exhibit excellent microwave dielectric characteristics: εr = 33.91, Q×f = 64,136 GHz, and τf = − 50.57 ppm/°C. Furthermore, in order to improve the temperature coefficient of resonant frequency (τf values close to zero) for the ZnTi0.990Mo0.010Nb2O8 ceramics, the TiO2 and laminated co-firing technique were used to adjust the comprehensive microwave dielectric characteristics of the ZnTiNb2O8 system. When the mass fraction of the TiO2 layer reaches 0.03 wt% after sintering at 1150 °C, the tri-layer structural ZTMN-0.03TO-ZTMN ceramics obtain outstanding microwave dielectric characteristics: εr = 41.52, Q×f = 50,827 GHz, and τf = − 2.59 ppm/°C, and these characteristics make them potential for usage in 5G communications.

Ionic substitution effects on the structure-property relationship of Zn0.5Ti0.5NbO4 microwave dielectric ceramics

In the present study, ionic substitution strategies were adopted in ixiolite Zn 0·5 Ti 0·5 NbO 4 ceramics, where the Co 2+ and Ta 5+ cations were used to partially replace the Zn and Nb sites and to investigate the structural evolution and microwave dielectric performances. It is interesting to find that the substitution of Co 2+ and Ta 5+ cations both lead to the reduction of volume of the unit cell, however, the variations of chemical bond behaviors are different, which is explained by the Rietveld refinement method, normalized bond analysis, polyhedral stretching behaviors, and the changes of characteristic Raman peaks. Furthermore, based on the complex chemical bond theory calculation, the drop of dielectric constant within the solid solution limits is attributed to the decline of average bond ionicity value along with the increase of ionic substitution content; while the lattice stability and uniformity of grain growth are mainly responsible for the variations of Q f value. After exceeding the solid solution limits, the developments of dielectric performances of Zn 0·5 Ti 0·5 NbO 4 ceramics are more sensitive to the regulation of the secondary rutile phase. More importantly, the intrinsic dielectric properties analysis indicates that the absorption of structural phonon oscillation mainly causes the dielectric response in the microwave range.

Effect of Cu2+ substitution on the crystal structure, bond properties, and microwave performance of ZnTiNb2O8 ceramics

Dense Zn1-xCuxTiNb2O8 (x = 0.000, 0.002, 0.005, 0.007, 0.010, 0.020, 0.030, 0.040, and 0.050) ceramics were synthesized using a traditional solid-state reaction approach. In the past, CuO was employed as a sintering additive to reduce the sintering temperature. In this paper, the influence of Cu2+ substitution on crystal structure, microstructure, bond properties, and microwave performance in ceramics with rutile-like structure was thoroughly investigated for the first time. According to the microstructures investigation, a moderate degree of Cu2+ substitution was shown to be useful for establishing uniform grain size and limiting dielectric loss. Furthermore, Raman spectroscopy and complex chemical bond theory were used to identify the relationship between microwave performance and intrinsic components in order to further investigate the influence mechanism of microwave performance. The results support that the determining factor of εr value is ionic polarizability. The major factors of Q×f value are the total lattice energy and the FWHM of Ag(2) stretch mode in Raman spectra. In addition, the τf value is mainly regulated by the total bond energy. Especially, the Zn1-xCuxTiNb2O8 (x = 0.005) ceramic exhibited excellent microwave performance: εr = 31.55, Q×f = 62,045 GHz, and τf = −48.01 ppm/°C, making it a viable choice for microwave components.

New temperature stable YbTaO4 microwave dielectric ceramic with monoclinic structure

A new temperature-stable YbTaO4 ceramic with monoclinic structure was fabricated using the traditional solid-state method. The relationship between the structure and properties was studied using Rietveld refinement and complex chemical bond theory. The change in the dielectric constant of YbTaO4 ceramics is affected by the relative density. The values of the dielectric constant obtained by complex chemical bond theory and the Clausius–Mossotti equation are consistent with the experimental results. Research based on complex chemical bond theory indicates that Ta–O bonds have the highest bond energy and bond iconicity, which have a decisive influence on dielectric polarizabilities and dielectric performance. The microwave dielectric properties of the YbTaO4 ceramic sintered at 1675 °C were obtained as follows: dielectric constant εr = 18.52, quality factor Q×f = 21928 GHz, and temperature drift τf = 1.28 ppm/°C.

High Q×f values of Zn-Ni co-modified LiMg0.9Zn0.1-xNixPO4 microwave dielectric ceramics for 5G/6G LTCC modules

In this work, Zn-Ni co-modified LiMg0.9Zn0.1-xNixPO4 (x = 0–0.1) microwave dielectric ceramics were fabricated using a solid state synthesis route. Rietveld refinement of the XRD data revealed that all ceramic samples have formed a single phase with olivine structure. SEM images showed that the samples have a dense microstructure, that agrees with the measured relative density of 97.73 %. Based on the complex chemical bond theory, Raman and infrared reflectance spectra, we postulate that εr is mainly affected by the ionic polarizability, lattice and bond energy, while P-O bond plays a decisive role in Q×f and τf value. Optimum properties of Q×f ~ 153,500 GHz, εr ~ 7.13 and τf ~ −59 ppm/°C were achieved for the composition LiMg0.9Zn0.06Ni0.04PO4 sintered at 875 ℃ for 2 h. This set of properties makes these ceramics an excellent candidate for LTCC, wave-guide filters and antennas for 5 G/6 G communication applications.

A new type of microwave dielectric ceramic based on K2O–SrO–P2O5 composition with high quality factor and low sintering temperature

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.