Complex Chemical Bond Theory Research Articles

Microwave dielectric properties of Mg1.8R0.2Al4Si5O18 (R = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn) cordierite ceramics and their application for 5G microstrip patch antenna

In this work, the effects of divalent ions on the phase structure, microstructure, and microwave dielectric properties of Mg1.8R0.2Al4Si5O18 (R = Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn) cordierite ceramics were investigated. Complex chemical bond theory, Raman spectrum and infrared reflectance spectrum were employed to understand the relationship among structural characteristics, vibration modes and microwave dielectric properties for alkaline earth and transitional metal divalent elements doped cordierite ceramics. The optimal microwave dielectric properties were obtained for Mg1.8Ni0.2Al4Si5O18 with εr of 4.53, Q×f of 61,880 GHz and τf of -32 ppm/℃. Finally, a 5G-Sub 6GHz patch antennas with a central frequency of 4.91 GHz was successfully designed and fabricated using a Mg1.8Ni0.2Al4Si5O18 substrate. The antenna exhibited excellent performance with a gain of 5.83 dBi and an efficiency of 76 %, showing promise to be employed in 5 G/6G millimeter-wave communication technology.

A low‐permittivity microwave dielectric ceramic BaZnP2O7 and its performance modification

AbstractComplex pyrophosphates compounds have attracted much attention as promising candidates for substrate applications. In the work, a low‐permittivity BaZnP2O7 ceramic was synthesized through solid‐state reaction. The pure phase BaZnP2O7 was crystallized in the triclinic P−1 space group. Excellent microwave dielectric properties of the BaZnP2O7 ceramic with εr = 8.23, Qf = 56170 GHz, and τf = −28.7 ppm/°C were obtained at 870°C for 4 h. The substitution of Mg2+ for Zn2+ was found to have positive effects on grain morphology and dielectric properties. Optimized performance of εr = 8.21, Qf = 84760 GHz, and τf = −21.9 ppm/°C was yielded at 900°C for the BaZn0.98Mg0.02P2O7 ceramic. Intrinsic dielectric properties of BaZn1‐xMgxP2O7 ceramics were studied via Clausius–Mossotti equation and complex chemical bond theory.

Sintering behavior, infrared spectra and microwave dielectric characteristics analysis for Ce2Zr3(MoO4)9 ceramics achieved by reaction-sintering method

Ce2Zr3(MoO4)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 εr= 10.1, Q×f= 69,705 GHz and τf= −6.34 ppm/°C, sintered at 850 °C.

Effects of (Mg1/3Sb2/3)4+ substitutions on the sintering behaviors and microwave dielectric properties of Li2Mg4Zr1−x(Mg1/3Sb2/3)xO7 ceramics

In this work, a series Li2Mg4Zr1−x(Mg1/3Sb2/3)xO7 (x = 0.10–0.25) ceramics were synthesized using the classical solid-state reaction method. The effects of (Mg1/3Sb2/3)4+ in the microstructures, sintering behaviors, and microwave dielectric properties of Li2Mg4Zr1−x(Mg1/3Sb2/3)xO7 ceramics were investigated systematically. XRD analyses indicate that all samples were the rock-salt structure with the Fm-3m 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 Li2Mg4Zr1−x(Mg1/3Sb2/3)xO7 ceramics were analyzed in details. By adding proper content of (Mg1/3Sb2/3)4+, the optimal dielectric performance of ɛr = 12.29, Q × f = 153,140 GHz, and τf = −17.7 ppm/°C were obtained in the Li2Mg4Zr0.8(Mg1/3Sb2/3)0.2O7 materials at 1600 °C for 4 h. The quality factor is more than 100 THz, which indicates that the Li2Mg4Zr0.8(Mg1/3Sb2/3)0.2O7 ceramic is a good candidate for the highly selective filters or microwave resonators.

Bond characteristics and microwave dielectric properties of high‐Q materials in li‐doped Zn3B2O6 systems

AbstractThe bond characteristics, Raman spectroscopy, and microwave dielectric properties of Zn3‐xLi2x(BO3)2 ceramics prepared by solid‐state reaction method were investigated. According to the complex chemical bond theory, the bond ionicity and lattice energy of the B–O bond were proved to contributed more to the electric polarization and phase structure stability than that of A‐site bond. Thus, the B–O bond had a dominant effect on the dielectric constant and Q × f values. The optimization of the τf value can be attributed to the bond valence. Moreover, the shift and full width at half maximum of the Raman peak were closely related to the dielectric constant and Q × f values, respectively. On the whole, Li+ substitution contributed greatly to improve the temperature stability and reducing the dielectric loss of Zn3‐xLi2x(BO3)2 ceramics. Additionally, Zn2.99Li0.02(BO3)2 ceramics sintered at 850 °C exhibited satisfactory microwave dielectric properties of εr=6.59, Q × f=122,030 GHz, τf=−76.9 ppm/°C, and had good chemical compatibility with silver.

Phase evolution, crystal structure, and microwave dielectric properties of gillespite‐type ceramics

AbstractA gillespite‐structured MCuSi4O10 (M = Ba1‐xSrx, Sr1‐xCax) ceramics with tetrahedral structure (P4/ncc) were prepared by solid‐state reaction method. X‐ray diffraction and thermogravimetry with differential scanning calorimetry (TG‐DSC) were employed to study the phase synthesis process of BaCuSi4O10. Pure BaCuSi4O10 phase was obtained at 1075°C and decomposed into BaSiO3, BaCuSi2O6, and SiO2 when calcined at 1200°C. The relationships between the crystal structure and microwave dielectric properties of MCuSi4O10 ceramics were revealed based on the Rietveld refinement and P‐V‐L complex chemical bond theory. The dielectric constant (εr) decreased linearly with decreasing total bond susceptibility and ionic polarizability. Quality factor (Q × f) was closely dependent on bond strength and lattice energy. The temperature coefficient of resonant frequency (τf) was controlled by the stability of [CuO4]6− plane in MCuSi4O10. Optimum microwave dielectric properties were obtained for SrCuSi4O10 when sintered at 1100°C for 3 hours with a εr of 5.59, a Q × f value of 82 252 GHz, and a τf of −41.34 ppm/°C. Thus, SrCuSi4O10 is a good candidate for millimeter‐wave devices.

Bond characteristics and microwave dielectric properties on Zn3-xCux(BO3)2 ceramics with ultralow dielectric loss

The crystal structure and microwave dielectric properties of Zn3-xCux(BO3)2 (x = 0–0.12) ceramics prepared via a traditional solid-state reaction method were investigated by means of X-ray diffraction (XRD) utilizing the Rietveld refinement, complex chemical bond theory, and Raman spectroscopy. XRD showed that all samples were single phase. The samples maintained a low permittivity, even at higher Cu2+ contents, which is conducive to the shortening of signal delay time, and intimately related to the average bond ionicity and Raman shift. Moreover, proper Cu2+ substitution greatly reduced the dielectric loss associated with the lattice energy. Cu2+ entering the lattice optimized the temperature coefficient of resonance frequency (τf) values and improved the temperature stability of samples by affecting the bond energy. Optimal microwave dielectric properties were: εr = 6.64, Q × f = 160,887 GHz, τf = −42.76 ppm/°C for Zn2.96Cu0.04(BO3)2 ceramics sintered at 850 °C for 3 h, which exhibited good chemical compatibility with silver and are therefore good candidate materials for Low temperature co-fired ceramic applications.

Bond characteristics and microwave dielectric properties of (Li0.5Ga0.5)2+ doped Mg2Al4Si5O18 ceramics

Cordierite ceramic is one kind of important electronic materials for radio frequency circuit. In this work, Mg2-x (Li0.5Ga0.5)xAl4Si5O18 (0 ≤ x ≤ 0.1) ceramics with pure cordierite phase, were successfully synthesized via the traditional solid state reaction method. The dependence of microwave dielectric properties on the crystal structure was analyzed in detail by the complex chemical bond theory (P–V-L theory) and classical dielectric polarizability theory. The dielectric constant (εr) was mainly related to the density, bond ionicity and ionic polarizability of Mg2-x (Li0.5Ga0.5)xAl4Si5O18 ceramics. The quality factor (Q × f) was in relationship to the lattice energy, atomic packing fraction and centrosymmetry of [Si4Al2O18] hexagonal ring in cordierite crystal structure. The temperature coefficient of resonant frequency (τf) value was dominated by the bond energy and distortions of [MgO6] octahedron. The maximum values of Q × f = 50,560 GHz and εr = 4.72 were obtained for undoped Mg2Al4Si5O18 and Mg1.98Li0.01Ga0.01Al4Si5O18, respectively.

Correlation between experimental and theoretical study of scheelite and wolframite-type tungstates

Structural and optical properties of AWO4(A=Ba, Sr, Ca, Mg, and Zn) ceramics were investigated. The structural analysis confirmed the scheelite-type tetragonal structure for (A=Ba, Sr and Ca)WO4 and wolframite-type monoclinic structure for (A=Zn and Mg)WO4 compounds. The experimentally observed optical band gap (Eg) found to be in the range of 4.17–5.92 eV agree with those calculated with the help of density functional theory. A decrease in band gap value with the decrease in ionic radii of A2+ in the AWO4 compound was observed. An intense blue-green photoluminescence emission was observed for these materials and correlated with Eg. The environmental factor he calculated by complex chemical bond theory has been correlated with the broadening of PL excitation bands. The excitation spectra revealed that there subsists a negative relation between he and position of energy levels.

Chemical bond parameters, charge transfer band in Eu3+-activated La2Mo2O9 phosphors based on complex chemical bond theory

Charge transfer band (CTB) plays an important role for the phosphors in the improvement of luminescence intensities, as low light absorption coefficient of the luminescence centers of the rare earth ions. Here, Eu3+-activated La2Mo2O9 phosphors were prepared by hydrothermal approach followed by calcination. Due to the special preparation process, the CTB of the phosphors could be effectively excited to get a very pure red emission. The structure of La2Mo2O9 was characterized. The field environmental factors (he) of La2Mo2O9:Eu3+ crystals were calculated based on complex chemical bond theory. The light absorption property of the MoO78− group was studied. The results indicated that the luminescence of the CTB originated from the three parts like Eu3+-O2-, α-Mo6+-O2- and β-Mo6+-O2-. Moreover, the FE-SEM micrographs, the photoluminescence properties and the decay time of La2Mo2O9:Eu3+ phosphors with different doping concentration were analyzed, which will further be promoting the development of the Eu3+-activated La2Mo2O9 phosphors.

Synthesis, lattice energy and microwave dielectric properties of BaCu2-xCoxSi2O7 ceramics

BaCu2-xCoxSi2O7 solid solutions with orthorhombic structure (Pnma) were prepared by solid-state reaction method. The phase synthesis process, structural evolution and microwave dielectric properties of BaCu2-xCoxSi2O7 ceramics were investigated. Single BaCu2Si2O7 phase was obtained when calcined at 950 °C for 3 h and was decomposed into BaCuSi2O6 phase when calcined at 1075 °C for 3 h. The sintering process was effectively promoted when Cu2+ was replaced by Co2+ and the maximum solubility of BaCu2-xCoxSi2O7 was located between 0.15 and 0.20. P-V-L complex chemical bond theory and Raman spectra were used to explain the structure-property correlations of BaCu2-xCoxSi2O7 ceramics. The corrected dielectric constant (εr-corr) of BaCu2-xCoxSi2O7 ceramics decreased monotonously with the susceptibility (Σχμ) and ionic polarizability of primitive unit cell. The quality factor (Q × f) increased with bond strength and lattice energy (Ucal), especially the lattice energy of the Si-O bond. The temperature coefficient of resonant frequency (τf) was determined by the susceptibility and lattice energy of the Cu/Co-O bond. The following optimum microwave dielectric properties were obtained at x = 0.15 when sintered at 1000 °C for 3 h: εr = 8.45, Q×f =58958 GHz and τf = -34.4 ppm/°C.

Structure and microwave dielectric properties of Li2Mg3Ti1-x(Al1/2Nb1/2)xO6 ceramics

Aiming to establish relationships between intrinsic structure factors and dielectric characteristics, a series of Li2Mg3Ti1-x(Al1/2Nb1/2)xO6 (x = 0.0, 0.04, 0.08, 0.12, 0.16, 0.20) ceramics were synthesized to investigate the influences of (Al1/2Nb1/2)4+ substitution on the dielectric properties of Li2Mg3TiO6 ceramics. The XRD and SEM results revealed that the pure rock salt phase (space group: Fm-3m) with a dense microstructure could be obtained with increasing the (Al1/2Nb1/2)4+ concentration, which is accompanied by an increase in the grain size from 11.69 to 22.81 μm. Meanwhile, some intrinsic factors, such as the average ionic polarizability, bond energy, packing fraction and lattice energy were calculated according to the complex chemical bond theory and refinement results. The unusual change in the dielectric constant (εr) was explained by the combined effects of the average ionic polarizability and relative density. The variation in the quality factor (Q × f) was ascribed to the packing fraction and lattice energy. The temperature coefficient of the resonant frequency (|τf|) reduced gradually with the increase in the octahedral bond energy, which enhanced the system thermal stability. Particularly, the Li2Mg3Ti0.92(Al1/2Nb1/2)0.08O6 sample exhibited outstanding dielectric characteristics:εr = 15.256, Q × f = 174,300 GHz and τf = −19.97 ppm/°C.

Structure, bond characteristics and microwave dielectric properties of new A0.75Ti0.75Ta1.5O6 (A[dbnd]Ni, Co, Zn and Mg) ceramics based on complex chemical bond theory

Tri-rutile structured A0.75Ti0.75Ta1.5O6 (ANi, Co, Mg, Zn) ceramics were synthesized using traditional solid reaction method. The crystal structures were studied by X-ray diffraction in conjunction with Rietveld refinement analysis. Based on the complex chemical bond theory and crystallographic data, some principle chemical bond characteristics such as bond ionicity, lattice energy, bond energy and coefficient of thermal expansion of complex A0.75Ti0.75Ta1.5O6 ceramics were obtained through quantitative calculation. The calculated results provided useful information to clarify the correlations between chemical bond characteristics and microwave dielectric properties of A0.75Ti0.75Ta1.5O6 ceramics. The dielectric constant was closely associated with the ionicity of TaO bond, and the Q × f values were correlated with the lattice energy of TaO bond. The τf values were affected by the bond energy of TaO bond and the coefficient of thermal expansion of AO bond.

Gd2Zr3(MoO4)9 microwave dielectric ceramics with trigonal structure for LTCC application

AbstractGd2Zr3(MoO4)9 is a double trigonal molybdate crystallized in the space group . The optimal microwave dielectric properties were achieved via solid‐state reaction at 725°C for Gd2Zr3(MoO4)9 ceramics: εr = 11.17, Q × f = 57 460 GHz, τf = −31.91 ppm/°C. The three‐dimensional framework type structure is formed by mixed MoO4 tetrahedron and ZrO6/GdO9 polyhedron. The analysis based on complex chemical bond theory shows that the Mo–O bonds account for majority contribution to controlling microwave dielectric properties. The MoO4 tetrahedron and ZrO6 octahedron stabilize the crystal structure by strong binding ability. As it was shown by Raman spectroscopy, the Raman‐active vibrations primarily originate from MoO4 tetrahedron, similarly to molybdate analogies.

Combined synthesis methods for producing LaNbO4 ceramics and investigation of microwave dielectric properties based on complex chemical bond theory

Highly reactive LaNbO4 nanopowders with particle sizes of 20–50 nm were synthesized at 700 °C through the citric gel process. Niobium oxalate was used as raw material for the first time, which provided a more convenient and precise way for the whole process. In order to reduce the sintering temperature of the LaNbO4 ceramic without introducing other impurities, LaNbO4 nanopowders were added to densify the ceramic at a lower temperature. When different mass percentage x wt% (x = 0, 0.5, 1, 2, 4) of the nanopowders were added, the sintering temperature of LaNbO4 ceramics prepared through conventional solid-state reaction method was successfully lowered more than 100 °C. The obtained ceramics presented good microwave dielectric properties. Rietveld refinement was used to investigate the crystal structure of the samples. The relationships between bond ionicity and dielectric constant (εr), lattice energy and the Q×f0 value, bond energy and the temperature coefficient of resonant frequency (τf) were calculated and analyzed with P–V-L theory. LaNbO4 ceramics with 1 wt% LaNbO4 nanopowders additive sintered at 1275 °C for 4 h showed excellent microwave dielectric properties: εr = 20.26, Q×f0 = 59740 GHz and τf = 7.44 ppm/°C.

Correlation between structure characteristics and dielectric properties of Li2Mg3-xCuxTiO6 ceramics based on complex chemical bond theory

A series of Li2Mg3-xCuxTiO6 (x = 0.00–0.20) ceramics were synthesized by a simple solid-state reaction. The influences of Cu2+ substitution on the microwave dielectric characteristics, structure characteristics and morphology of Li2Mg3TiO6 ceramics were investigated. The XRD results demonstrated that all samples displayed the pure Li2Mg3TiO6 phase with rock salt structure. The SEM results exhibited that a microstructure evolution from porous structure to nearly compact structure appeared with increasing Cu2+ content, indicating that the pores originated from lithium volatilization could be suppressed by Cu2+ substitution. Subsequently, the dependence of microwave dielectric properties on intrinsic factors was evaluated based on refinement results and P–V–L theory. The monotonic increase of dielectric constant (εr) was mainly correlated with the polarizability. The variation of quality factor (Q × f) was dependent on the total systematic lattice energy and packing fraction. In addition, the evolution tendency of the temperature coefficient of resonant frequency (τf) was explained by the linear thermal expansion coefficient α and EMg/Cu–O bond energy. All results suggested that the intrinsic factors play decisive roles on dielectric characteristics.

Raman, complex chemical bond and structural studies of novel CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x=0-0.1) ceramics

Low permittivity CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x = 0-0.1) ceramics were synthesized via the solid-state reaction process for the first time. The Rietveld refinement, complex chemical bond theory and Raman spectra were introduced to analyze the effects of Mn2+/Zn2+ co-substitution to microwave dielectric properties. XRD spectra indicate the CaMg1-x(Mn1/2Zn1/2)xSi2O6 ceramics processed the pure phase of CaMgSi2O6 when x ≤ 0.02 and a small volume of secondary phase Ca2MgSi2O7 for 0.04 ≤ x ≤ 0.1. The variation of εr can be put down to average bond iconicity and Raman shift. Total lattice energy and packing fraction are main influence factor of the Q×f value. The monotonous decrease of τf is associated with total bond valence and full width at half maximum of Raman peak. Additionally, CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x = 0.02) ceramics sintered at 1280 °C for 3 h exhibited excellent microwave dielectric properties of εr = 8.16, Q×f = 70187, τf = −38.48 ppm/°C.

Synthesis, crystal structure and microwave dielectric properties of self-temperature stable Ba1-xSrxCuSi2O6 ceramics for millimeter-wave communication

Ba1-xSrxCuSi2O6 compounds with a tetrahedral structure (I41/acd) were prepared through the solid-state reaction method. The phase building process, structural evolution and microwave dielectric properties of Ba1-xSrxCuSi2O6 were investigated. Single BaCuSi2O6 phase can be obtained when calcined at 1050 °C for 3 h or 950 °C for 10 h. The substitution of Ba2+ by Sr2+ can effectively promote the sintering process and the maximum solubility of Ba1-xSrxCuSi2O6 was located between 0.25 and 0.30. Rietveld refinement, Raman-spectra and P-V-L complex chemical bond theory were used to explain the correlations between the crystal structures and microwave dielectric properties. The dielectric constant was dominated by the susceptibility (Σχμ) and ionic polarizability. The quality factor (Q × f) was determined by the bond strength, packing fraction and lattice energy, especially the Si-O bond. The susceptibility of Cu-O bond and Si-O bond played an important role in controlling the temperature coefficient of the resonant frequency (τf). A near zero τf value was obtained at x = 0–0.10 and the optimum microwave dielectric properties for Ba1-xSrxCuSi2O6 were achieved at x = 0.20 when sintered at 1000 °C for 3 h: εr = 8.25, Q × f = 47616 GHz and τf = −9.6 ppm/oC.

Low-temperature sintering mechanism and microwave dielectric properties of ZnAl2O4-LMZBS composites

A new low-temperature-cofired ceramics (LTCC) material that consists of ZnAl2O4 ceramics and highly crystallized Li–Mg–Zn–B–Si (LMZBS) glass has been synthesized by solid state reaction. The LMZBS glass acts as a sintering aid to reduce sintering temperature of ZnAl2O4 ceramics from more than 1400 °C–930 °C. The influences of the LMZBS glass content on the phase composition, crystallization activation energy and microwave dielectric properties of ZnAl2O4 ceramics were investigated. Based on the Rietveld refinement and complex chemical bond theory, the influence of LMZBS glass on the structure and bond length of ZnAl2O4 ceramics were analyzed. X-ray diffractometer results showed that the LMZBS glass crystallized forming Mg2B2O5 and Li2ZnSiO4, and did not react with ZnAl2O4 ceramics. As LMZBS glass was increased, Mg2B2O5 and Li2ZnSiO4 gradually dominated the composite and ZnAl2O4 phase decreased. Meanwhile, the flexural strength (σ), dielectric constant (εr) and temperature coefficient of resonant frequency (τf) demonstrated gradually increase, whereas the quality factor (Q×f) presented a trend of rise first and then fall. The composite which the mass ratio of ZnAl2O4 ceramics to LMZBS glass is 1:2 can be sintered at 930 °C for 3h exhibited optimal microwave dielectric properties: εr = 7.4, Q×f = 34,100 GHz, τf = −43.99 ppm/°C and flexural strength (σ = 141 MPa). In addition, the new LTCC material can be co-fired with Ag electrode that have high electrical conductivity.

Structure, bond characteristics and Raman spectra of CaMg1-Mn Si2O6 microwave dielectric ceramics

Abstract The CaMg1-xMnxSi2O6(x = 0–0.08)ceramics were reported here for the first time. The relationships among structural characteristics, vibrational modes and dielectric properties for the ceramics were researched based on complex chemical bond theory and Raman vibrational spectroscopy. The formation of a single phase with clinopyroxene structure when x = 0 to 0.08 was detected by X-ray diffraction. The monotonous increase of e r is ascribed to the average bond covalency, polarizability and Raman shift. The Q × f value is influenced by total lattice energy and full width at half maximum of Raman spectra which are both connected with the intrinsic loss. The variation of τ f is related to thermal expansion coefficient and M1-site bond valence. Furthermore, the CaMg0.98Mn0·02Si2O6 ceramic sintered at 1300 °C possessed optimal microwave dielectric properties of e r = 8.01, Q × f = 83469 GHz and τ f = −45.27 ppm/°C.