Bimetallic sulfides embedded into porous carbon composites with tunable magneto-dielectric properties for lightweight biomass- reinforced microwave absorber

Currently, biomass-derived porous carbon materials have great potential for the development of advanced microwave absorbing materials (MAMs) with lightweight, high performance, wide effective bandwidth (EAB), and thin matching thickness. Herein, we reported low-cost, high-performance MAMs for the successful anchoring of Cu-based bimetallic sulfides CuCo₂S₄@CoS₂ on biomass porous carbon (BPC) derived from pistachio shells using a simple carbonization, hydrothermal, and electrostatic self-assembly method. The results demonstrate that the prepared BPC@CuCo₂S₄@CoS₂ composite exhibits excellent microwave absorption due to its balanced impedance matching and the combined effect of conductive loss, dipole polarization, interfacial polarization, dielectric loss, and magnetic loss. To be precise, the minimum reflection loss (RL_min) of BPC@CuCo₂S₄@CoS₂ reaches −64.2 dB at a packing load of 20 wt%, with an EAB of 6.6 GHz and a thickness of 2.3 mm. This work provides new insights into the study of copper-based bimetallic sulfide and BPC composites in MAMs.     

Crystallographic characteristics and microwave dielectric properties of Ni-modified MgTa2O6 ceramics

Ni²⁺ modified MgTa₂O₆ ceramics with a trirutile phase and space group P4₂/mnm were obtained. The correlations between crystallographic characteristics and microwave dielectric performance of MgTa₂O₆ ceramics were systematically studied based on the chemistry bond theory (PVL theory) for the first time. The results indicate that the introduction of Ni²⁺ causes a change in polarizability and the Mg–O bond ionicity, which contributes to the variation of dielectric constant. Moreover, the lattice energy, and packing fraction, full width at half maximum of the Raman peak of Ta–O bond, as the quantitative characterization of crystallographic parameters, regulate the dielectric loss of MgTa₂O₆ ceramics in GHz frequency band. In addition, the study of sintering behavior shows that the densification and micromorphology are the crucial factors affecting the microwave dielectric performance. Typically, Ni²⁺ doping on the A-site of MgTa₂O₆ can effectively promote the Q × f values to 173,000 GHz (at 7.43 GHz), which ensures its applicability in 5G communication technology.     

Low‐Temperature Sintering Li2MoO4/Ni0.5Zn0.5Fe2O4 Magneto‐Dielectric Composites for High‐Frequency Application

The coexistence of Li₂MoO₄ (LMO) and Ni_0.5Zn_0.5Fe₂O₄ (NZO) has been proven and their low‐temperature‐sintered magneto‐dielectric composites (1?x)LMO–xNZO (volume fraction factor x = 0.1, 0.3, 0.5, 0.7) were prepared by the conventional solid‐state reaction method and were sintered below 700°C. It is found that the optimal sample (x = 0.5) has good and relatively stable magneto‐dielectric performance in the frequency range from 10 MHz to 1 GHz with permittivity between 7.14 and 6.84, dielectric loss tangent between 0.09 and 0.02, and permeability between 5.23 and 3.30, magnetic loss tangent between 0.06 and 0.65, respectively. Furthermore, the verified chemical compatibility with silver indicates that the LMO–NZO ceramics are potential for low‐temperature cofired ceramic application and their multifunctional magneto‐dielectric properties also make them for potential applications in electronic devices.     

Comparison of microwave dielectric behavior between Bi1.5Zn0.92Nb1.5O6.92 and Bi1.5ZnNb1.5O7

The microwave dielectric, Bi_1.5ZnNb_1.5O₇ exhibits low-temperature dielectric relaxation. To find the origin of the dielectric relaxation of Bi_1.5ZnNb_1.5O₇, we studied the structure and dielectric behavior of Bi_1.5ZnNb_1.5O₇ in detail. The Bi_1.5ZnNb_1.5O₇ is not composed of a single phase pyrochlore structure. Instead, it consists of unusual structure of Bi_1.5Zn_0.92Nb_1.5O_6.92 and ZnO. The ZnO is distributed evenly in the grain and at the boundary of the Bi_1.5Zn_0.92Nb_1.5O_6.92 structure. Many small voids (<1 μm) were observed in the samples due to the loss of volatile Bi during sintering. The Bi_1.5Zn_0.92Nb_1.5O_6.92 exhibited a broad dielectric relaxation between 100 and 400 K at 1.8 GHz, peaking around 230 K. The Fourier transformation IR spectra predict that dielectric relaxation may occur near room temperature during extremely high frequencies (THz). The substitutional point defects in Bi_1.5Zn_0.92Nb_1.5O_6.92 provide room for dielectric relaxation at microwave frequencies. The low quality factor Q × f (∼520 GHz) of Bi_1.5Zn_0.92Nb_1.5O_6.92 results from both the dielectric relaxation of the material and the voids within its microstructure. The presence of ZnO phase in the Bi_1.5ZnNb_1.5O₇ produces interstitial defects that further enhance the dielectric relaxation with reduced quality factor Q × f (∼426 GHz).     

Fabrication of hierarchical PANI@W-type barium hexaferrite composites for highly efficient microwave absorption

Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo₂Fe₁₆O₂₇ is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications.     

Dielectric regulation of high-graphitized fine ash wrapped cube-like ZnSnO3 composites with boosted microwave absorption performance

Intrinsic dielectric properties and tuning conductivity play important roles in microwave absorption. Novel multi-interfaced ZnSnO₃@ fine ash (ZSFA) composite was successfully synthesized by coating cube-like ZnSnO₃ particles with highly graphitized gasification fine ash. After hydrothermal reaction and Ostwald ripening process, fine ash was tightly wrapped around the assembly of ZnSnO₃ particles. Related electromagnetic parameters and dielectric dissipation ability were discussed with different mass additions. Owing to the strong polarization relaxation, special conductive network, and multi-interface structural design, the as-synthesized ZSFA exhibited adjustable dielectric loss behaviors and efficient microwave absorption ability. When 50% mass added, the maximum reflection loss value of the obtained ZSFA-2 is ?47.8 dB at 2.5 mm thickness, showing the enhanced dielectric loss ability. Meanwhile, the widest effective absorption bandwidth (RL ≤ ?10 dB) can cover 7.0 GHz (11.0–18.0 GHz) at a thickness of only 2.2 mm, which included the entire Ku band. This unique pure dielectric composite exhibited high-performance electromagnetic wave attenuation property and broadband frequency response, thereby providing a new approach to the production of a superior microwave absorber.     

Investigation on microwave absorption characteristics of ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-Polyaniline Co-polymers

In this study, ternary MWCNTs/CoFe₂O₄/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe₂O₄ and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating magneto-dielectric particles with conductive co-polymers improved the permittivity and dielectric constant, accordingly affecting the impedance matching characteristic and attenuation constant performance. Moreover, exchange coupling behavior was found significant impacts on the microwave absorption properties. PA@MW/F/C coated nanocomposite revealed the maximum reflection loss of ?90 dB at 13.8 GHz with 4 GHz effective bandwidth and 1.5 mm thickness. Due to the enhanced interfacial polarization, impedance matching and exchange coupling effects of the as-prepared nanocomposite, it owns excellent microwave absorption properties, which can be applied as an absorber with distinguishing features (strong absorption, thin thickness, and broadest effective bandwidth).     

Enhanced dielectric and microwave absorption properties of Cr/Al2O3 coatings deposited by low‐power plasma spraying

Low‐power plasma‐sprayed Cr/Al₂O₃ coatings have been developed for their potential application as broad bandwidth, thin thickness, lightweight, and strong microwave‐absorbing materials. The dielectric and microwave absorption properties of the as‐sprayed coatings were studied in the X‐band (from 8.2 to 12.4 GHz). High complex permittivity of the coatings was obtained because of a large number of internal boundaries and the conductive networks. Meanwhile, a significant enhancement of microwave absorption properties of the coating was achieved due to the enhanced interfacial polarization and conductance loss. The reflection loss (RL) <?10 dB of the Al₂O₃–15Cr coating was obtained from 9.8 to 11.4 GHz by choosing an appropriate coating thickness, and an optimal minimum reflection loss (RL_min) of ?45.35 dB was achieved at 10.3 GHz with a thin thickness of 1.32 mm.     

Enhanced magnetodielectric properties of Co2Z ferrite ceramics for ultrahigh frequency applications achieved via Cr3+ ion doping

Phase formation, microstructure, magnetic properties, and dielectric properties of Ba_1.5Sr_1.5Co₂Fe₍₂₃−_x)Cr_xO₄₁ (0.0 ≤ x ≤ 1.0) ceramics, in which Fe³⁺ ions were substituted by Cr³⁺ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr³⁺ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr³⁺ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm³. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr³⁺ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices.     

Structural,electromagnetic properties and broad microwave absorption bandwidth of SrFe12-2xCoxRuxO19

SrFe_12-2xCo_xRu_xO₁₉ become magnetically soft with Co and Ru doping. The magnetization is high, but the anistropic field becomes low. The FT-IR spectra suggest that Co and Ru substitute for Fe at the 4f1 site. At this site, the substitution of Co and Ru with low magnetic moments weakens the anisotropy. The sharp magnetic resonances observed in x = 0.3, 0.5 and 0.7 are due to the domain wall movement. The natural magnetic resonance frequency falls in the frequency of 2–18 GHz. The Co and Ru doping increases both the magnetic loss tangent and the dielectric loss tangent. The high magnetic and dielectric loss tangents are in favor of high attenuation factors. With good impedance matching and high attenuation factor, the microwave absorption properties are excellent in x ≥ 0.3. In x = 0.5, the bandwidth is 11.8 GHz centered at 10.5 GHz. In each x > 0.5 sample, the optimum bandwidth is broader than 9 GHz. In x = 1.1, at 1.9 mm, the absorption bandwidth is broader than 9 GHz from 9 GHz to higher than 18 GHz centered at 11.6 GHz. Compared with the advanced materials published in recent decades, the bandwidth of the present work are very competitive.     

Polyaniline-based networks combined with Fe3O4 hollow spheres and carbon balls for excellent electromagnetic wave absorption

Polyaniline (PANI)-based networks combined with Fe₃O₄ hollow spheres and carbon balls (FCP) for improved electromagnetic wave (EMW) absorption were investigated using an easy-to-industrialize solvothermal and physical method. Hollow structure Fe₃O₄ spheres with a lower density than that of the common solid sphere were prepared. As a thin and light magnetic material, Fe₃O₄ hollow spheres generate magnetic loss, carbon balls and PANI networks generate dielectric loss. The magnetic and conductive parts play appropriate roles in achieving complementarity in the EMW absorption. The relatively high specific surface area introduced by PANI networks promotes interfacial polarization and further supports dielectric loss. In conclusion, the above reasons provide multiple attenuation mechanisms. Samples FCP1 (?65.109 dB, at 12.800 GHz, 1.966 mm, from 5.6 to 18.0 GHz) and FCP2 (?61.033 dB, at 8.480 GHz, 3.328 mm, from 4.3 to 18.0 GHz) demonstrated a wide bandwidth, a small thickness, a minimum reflection loss (R_L), and a low loading ratio (25%) in paraffin-based composites. Specifically, their loading ration of 25% is much lower than the loading ratio of conventional materials (usually 50% and above). In addition, the bandwidth is excessively wide, above 12 GHz, possessing good absorption performance in continuous intervals with different thicknesses. Such excellent characteristics have rarely been reported in literature.     

Dielectric permittivity and microwave absorption properties of transition metal Ni and Mn doped SiC nanowires

In order to enhance the microwave absorption properties of SiC nanowires, two transition metals Ni and Mn were selected as doping elements to improve their electromagnetic parameters. The experimental results indicate that Ni and Mn as catalysts reduce the stacking defect density of SiC nanowires, which will weaken the interfacial polarization loss induced by stacking defects. However, they can increase the electrical conductivity of SiC nanowires and generate new impurity defects, thereby effectively improving the conductance loss and dipole polarization loss. Therefore, the dielectric loss of SiC nanowires is significantly enhanced, but they still do not have considerable magnetic loss capability. In addition, Ni and Mn doping also improves the impedance matching characteristics of SiC nanowires. Therefore, the microwave absorption ability of SiC nanowires is effectively enhanced. As the nanowire filling ratio is 20 wt%, the minimum reflection loss of the Ni_0.01Si_0.99C nanowire is −11.1 dB and the effective absorption bandwidth is 1.1 GHz (9.3–12.4 GHz) at a thickness of 2.8 mm; Mn_0.01Si_0.99C nanowires have a minimum reflection loss of −16.8 dB and an effective absorption bandwidth of 3.1 GHz (9.3–12.4 GHz) at a thickness of 2.8 mm.     

Microstructure and enhanced electromagnetic wave absorbing performance of Zn0.6Ni0.3Cu0.1Fe2O4 ferrite glass-ceramic

Here we introduce a controllable route for the efficient synthesis of Zn_0.6Ni_0.3Cu_0.1Fe₂O₄ ferrite glass-ceramic with enhanced electromagnetic wave (EMW) absorbing performance. By adding a certain amount of Zn, Ni, Cu and Fe oxides into the SiO₂–Al₂O₃–B₂O₃–CaO-R₂O glass system, the microstructure of three-dimensional dendritic ferrites combined with amorphous SiO₂-rich phase is constructed through a high-temperature melt and quenching route. The good EMW absorption performance is attributed to the unique combination of amorphous glass and spinel ferrite, which improves the impedance matching of the material and absorbs EMW by the dielectric loss and magnetic loss. Moreover, the dendritic ferrite crystal phase is compounded with the SiO₂-rich amorphous phase to form grain boundaries and crystal-amorphous interfaces, which enhances the interfacial polarization and builds multiple transmission-absorption mechanisms. The results show that the reflection loss peak value of the glass-ceramics containing 60 wt% Zn_0.6Ni_0.3Cu_0.1Fe₂O₄ spinel is ?42.16 dB with the sample thickness of 2 mm, and the effective absorption band range (reflection loss ≤ -10 dB) is 3.76 GHz (13.6–17.36 GHz) at 1.5 mm. This approach presents a scalable and low-cost solution that may be applied to the design of high-efficiency EMW consumption components in the future.     

Fabrication of Nd-doped Ni–Zn ferrite/multi-walled carbon nanotubes composites with effective microwave absorption properties

The electromagnetic materials are featured by good magnetic permeability and dielectric constant characteristics, which are of significant importance in solving the pollution problem of electromagnetic. In this study, after the complete of the use of sol-gel method, argon gas was then introduced for calcination, and eventually a new type of MWCNTs/Ni_0.5Zn_0.5Nd_0.04Fe_1.96O₄ composites was synthesized after the above mentioned procedures. The synthesized MWCNTs were able to be adsorbed on the surface of Ni_0.5Zn_0.5Nd_0.04Fe_1.96O₄ and could form a good conductive work of 3D. Also, the effect of additional MWCNTs on microwave absorption properties of MWCNTs/Ni_0.5Zn_0.5Nd_0.04Fe_1.96O₄ composites were also observed in this study. The results indicate that the additional MWCNTs function to significantly improve the microwave absorption property of MWCNTs/Ni_0.5Zn_0.5Nd_0.04Fe_1.96O₄. Through altering the amount of MWCNTs, the microwave attenuation performance and impedance matching coefficient of this electromagnetic materials can be effectively improved. The S2 sample presented a minimum reflection loss of ?35.05 dB when its thickness reached 1.6 mm, meanwhile, the effective absorption bandwidth achieved 4.55 GHz. The prepared composites perform well in microwave absorption, which can attribute to the reasonable ratio of composites as well as its interaction with both of the magnetic and dielectric components. This research paved the way for novel ideas to be put in the electromagnetic absorption materials with high-efficient.     

Nickel-modified zinc molybdate low temperature co-fired ceramics for two-dimensional beam splitting of array antenna in X-band

In this work, a new Zn_1-xNi_xMoO₄ (ZNMO) (x = 0.03) ceramic with low-dielectric constant, low-loss, and low-sintering temperature for X-band two-dimensional (2D) beam splitting is developed by solid-state reaction method. This ceramic has excellent microwave dielectric properties of ε_r = 8.5, Q × f = 28192 GHz, τ_f = ?60.2 ppm/°C. The effects of Ni²⁺ substitution on the microwave dielectric properties of the ZnMoO₄ ceramic are studied in detail through crystal structure analysis, Raman spectroscopy, and first-principles calculations. For the first time, an array antenna for X-band 2D electromagnetic beam splitting is designed by using this ceramic as a substrate. The effects of the dielectric constant and dielectric loss on the radiation efficiency of the array antenna are revealed. The normalized reflection amplitude and reflection phase of the unit cell exceed 0.97 and cover 360°, respectively. The function of 2D electromagnetic beam splitting is verified by the overall far-field pattern of the array antenna. This work has the opportunity to promote the development of LTCC and microwave dielectric ceramics.     

Electromagnetic wave absorbing properties of Cr2AlB2 powders and the effect of high-temperature oxidation

The electromagnetic (EM) wave absorbing properties of Cr₂AlB₂ powders and those after high-temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr₂AlB₂ with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (E_AB) is 4.4 GHz (13.0-17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding E_AB values, respectively, are 3.8 GHz (13.6-17.4 GHz, 1.7 mm), 4.1 GHz (13.5-17.6 GHz, 1.6 mm), and 4.4 GHz (13.0-17.4 GHz, 1.7 mm). With an absorber thickness of 1.5-4.0 mm, the E_AB with a RL value of less than −10 dB can be tuned in a broad-frequency range 5.0-18.0 GHz, which basically covers C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) bands. These results demonstrate that Cr₂AlB₂, as a high-efficient and oxidation-resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high-temperature oxidation.     

High-efficiency electromagnetic wave absorption of TiB2-SiCnws-SiOC synthesised using PDCs

A designed conductive nanoheterogeneous structure can boost interfacial polarisation and effectively enhance the wave absorption properties. Herein, maze-shaped nanoheterogeneous TiB₂-SiCnws-SiOC ceramics were synthesised via a polymer-derived ceramics (PDCs) approach for constructing a three-dimensional reticular structure. The addition of TiB₂ not only compensates for the lower conductivity, but also facilitates the growth of curved SiCnws. The results show that the addition of 20 wt% TiB₂ leads to favourable microwave absorption performance, with a minimal reflection coefficient of − 55.1 dB at 8.9 GHz and an effective absorption bandwidth of 4.2 GHz. This can be ascribed to the synergistic effect among polarisation loss, conduction loss, and microwave multiple reflection and scattering due to the unique structure. This study may contribute towards establishing multi-loss mechanisms and controllable dielectric properties in PDCs.     

Microstructure and Dielectric Properties of Nickel‐Doped Ba0.7Sr0.3TiO3 Ceramics Fabricated by Solgel Method

A study of phase transition, microstructure, and dielectric properties of Ba_0.7Sr_0.3Ti_1–xNi_xO₃ (BSTN) ceramics prepared by slow‐injection solgel technique with x ranging from 0 to 1 mol% is reported in this article. The as‐prepared BSTN material was calcined at 800 and 1000°C and subsequently sintered at 1100 and 1200°C, respectively. The optimized condition was found to be Ba_0.7Sr_0.3TiO₃ doped with 1 mol% nickel calcined at 1000°C and sintered at 1200°C having the lowest dielectric loss of 0.02 with a dielectric constant of 1603 which was measured at a frequency of 1 kHz at room temperature.     

Constructing hierarchical Ti3SiC2 layer and carbon nanotubes on SiC fibers for enhanced electromagnetic wave absorption

To enhance the absorption performance of silicon carbide fiber (SiC_f), hybrid fibers with a double shell structure (Ti₃SiC₂ and carbon nanotubes (CNTs)) on the SiC_f (CNT@Ti₃SiC₂@SiC_f) were successfully synthesized by the combination of molten salt method and floating catalytic chemical vapor deposition. A series of 10% weight fraction fibers reinforced paraffin samples was prepared to study the double coating influences on the electromagnetic wave (EMW) absorption performances. Coated by Ti₃SiC₂ and CNTs, the dielectric permittivity of hybrid fibers could be modulated in a quite wide range. The CNT@Ti₃SiC₂@SiC_f with a thickness of 3.8 mm showed a minimum reflection loss value of ?53 dB at 6.57 GHz, and the CNT@Ti₃SiC₂@SiC_f with a thickness of 2.5 mm presented a wide effective absorption bandwidth of 5.6 GHz (from 9 to 14.6 GHz). The highly improved EMW absorption performance of CNT@Ti₃SiC₂@SiC_f was attributed to the combination of conductive loss and dielectric loss aroused by interfaces. The excellent absorption performance provided the modified SiC_f with a high potential in the application of EMW absorbers.     

Sintering and Dielectric Properties of Li2O–B2O3–Al2O3–SiO2 Glass‐Added (Ca0.7Sr0.3O)1.03(Ti0.1Zr0.9)O2 for Copper Electrode

When 1.5 wt% of Li₂O–B₂O₃–SiO₂ and 1.5 wt% of Li₂O–B₂O₃–Al₂O₃ glass‐added (Ca_0.7Sr_0.3O)_1.03(Ti_0.1Zr_0.9)O₂ batch was ball milled for 10~30 h followed by sintering at 950°C in flowing N₂‐10%H₂ atmosphere, an apparent density of approximately 4.5 g/cm³, a dielectric constant of approximately 26, and a quality factor of roughly about 3300 GHz were demonstrated. A prolonged ball mill time thereafter significantly decreased both of the dielectric properties because of the enhanced reduction of the specimens during sintering. The apparent evidence of a material reaction between the dielectric material and the copper electrode was not observed.