High dielectric permittivity and percolative behavior of polyvinyl alcohol/potassium dihydrogen phosphate composites

A new kind of anhydrous, transparent, and flexible potassium dihydrogen phosphate (KH₂PO₄ or KDP)/polyvinyl alcohol (PVA) composite in the form of film (0.10 mm) has been prepared by solution casting technique. KDP is well dispersed in the polymer matrix as observed from the microstructural studies. Frequency and temperature dependent dielectric properties of the composites have been studied with varying KDP concentrations. The PVA/KDP composite films exhibited extraordinarily high relative permittivity ε′ ∼ 430 (80 times higher compared with pure PVA and even higher than KDP) near the percolation threshold (ϕ_C = 2.5 wt % KDP) with low dielectric losses (∼ 0.15) at 1 kHz and room temperature. Such flexible, low loss and high dielectric permittivity material has enormous importance for application in devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of SiC interphase on the mechanical,high-temperature dielectric and high-temperature microwave absorption properties of the SiCf/SiC/Mu composites

In this study, SiC interphase was prepared via a precursor infiltration-pyrolysis process, and effects of dipping concentrations on the mechanical, high-temperature dielectric and microwave absorption properties of the SiC_f/SiC/Mu composites had been investigated. Results indicated that different dipping concentrations influenced ultimate interfacial morphology. The SiC interphase prepared with 5 wt% PCS/xylene solution was smooth and homogeneous, and no bridging between the fiber monofilament could be observed. At the same time, SiC interphase prepared with 5 wt% PCS/xylene solution had significantly improved mechanical properties of the composite. In particular, the flexural strength of the composite prepared with 5 wt% PCS/xylene solution reached 281 MPa. Both ε′ and ε′′ of the SiC_f/SiC/Mu composites were enhanced after preparing SiC interphase at room temperature. The SiC_f/SiC/Mu composite prepared with 5 wt% PCS/xylene solution showed the maximum dielectric loss value of 0.38 at 10 GHz. Under the dual action of polarization mechanism and conductance loss, both ε′ and ε′′ of the SiC_f/SiC/Mu composites enhanced as the temperature increased. At 700 °C, the corresponding bandwidth (RL ≤ ?5 dB) of SiC_f/SiC/Mu composites prepared with 5 wt% PCS/xylene solution can reach 3.3 GHz at 2.6 mm. The SiC_f/SiC/Mu composite with SiC interphase prepared with 5 wt% PCS/xylene solution is expected to be an excellent structural-functional material.     

Eco-friendly poly(vinyl alcohol)/delaminated V2C MXene high-k nanocomposites with low dielectric loss enabled by moderate polarization and charge density at the interface

High-dielectric-constant (high-k) polymer/conductor composites with low dielectric loss are desirable for energy storage. However, high leakage currents from interfacial regions with high charge density are difficult to handle. In this work, high permittivity and low dielectric loss were achieved in poly(vinyl alcohol) (PVA)/V₂C MXene nanocomposite films fabricated by solution casting by taking advantage of the interfacial compatibility and moderate interfacial charge density of the nanocomposites. Water-soluble PVA was utilized as the polymer matrix. Delaminated V₂C MXene nanosheets with appropriate conductivity were prepared and used as the filler. The mild interface polarization of the nanocomposites was responsible for achieving favourable permittivity values. The small gap between the work functions of PVA and V₂C contributed to moderate interfacial charge density values and thus low dielectric loss values. A proportional correlation between the interfacial charge density and the conductivity of composites was also verified. The depth of charge injection from the MXene to PVA was found to be half of the interlamellar spacing of the delaminated MXene. The dependence of the electrical properties of the nanocomposites on the frequency and MXene content was also studied. The composite with 4 wt% MXene exhibited a permittivity of ~24 (16 times that of PVA) and a dielectric loss of ~0.14 (1.5 times that of PVA) at 1 kHz, as well as breakdown strength of ~31 MV m⁻¹ (63% of PVA). This work might enable environmentally friendly fabrication of promising composite dielectrics.     

Electromagnetic interference shielding properties of graphene quantum-dots reinforced poly(vinyl alcohol)/polypyrrole blend nanocomposites

Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low-cost material for EMI shielding applications.     

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO₃) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO₃ composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO₃ composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO₃ nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO₃ composite film shows that as the concentration of BaTiO₃ particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO₃ composites. The maximum hysteresis of the capacitive PVDF-BaTiO₃ (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO₃ (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.     

Reduced leakage current and improved multiferroic properties of 0.5((1−x)BLPFO-xPZT)-0.5PVDF composite films

0.5((1−x)Bi_0.8La_0.1Pr_0.2FeO₃ (BLPFO)-xPb(Zr_0.52Ti_0.48)O₃ (PZT))-0.5Polyvinylidene difluoride (PVDF) composite films with x variations 0.25, 0.40 and 0.50 were synthesized using two step mixing, followed by hot pressing. The structural, microstructural, dielectric, magnetic, ferroelectric and magnetodielectric properties of composite films have been systematically investigated. The measurement of the dielectric properties at 1 kHz shows that the dielectric loss (tan δ) decreases with increasing the volume fraction of PZT. The value of maximum room temperature ε_r ~78 and low tan δ ~0.061 for 0.5((1−x)BLPFO-xPZT)-0.5PVDF composite film with x=0.50 suggests its usefulness for capacitor applications. For predictions of effective dielectric constant of composite films experimental data were fitted with Lichtenecker model. Among all the composite films, the film with x=0.50 was found to exhibit smallest leakage current density ~7×10⁻⁸ A/cm² and hence improved electrical resistivity. The variation of magnetization with temperature indicates the presence of spin glass behavior along with the ferromagnetic component at 5 K. The value of remnant polarization (2P_r) is found to increase with increase of PZT content in composite films. In the present composite films a significant dependence of dielectric constant on magnetic field has been observed, and highest value of magnetodielectric response of 2.85% is observed for composite film with x=0.50.     

Flexible dielectric ZnO-doped reduced graphene oxide bionanocomposites from solution blending for potential application in bio-related devices

Biocompatible materials with high dielectric constant and low dielectric loss have applications in bio-related electronic devices. Development of flexible materials with those properties is still a challenge. In this work, electrospun membranes and films are prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) solutions, incorporated with a reduced graphene oxide-zinc oxide composite (rGO-ZnO). Blending CS with flexible PVA favors electrospinnability and mechanical properties. ZnO contributes to hinder agglomeration of conductive rGO sheets. The structural, mechanical, dielectric and electrical properties of the hybrid materials are investigated. Infrared spectroscopy reveals interaction between the filler and the polymeric components. For mats and films, the increase in rGO-ZnO content leads to lower crystallinity. The Young's modulus and stress at break values increase with increasing rGO-ZnO content. High dielectric constants (ε' = 132 to ε' = 166, at 10³ Hz), associated with low dielectric loss factor (tan δ = 0.02), are determined for the PVA/CS/rGO-ZnO films.     

Studies on NO2 gas sensing properties of sprayed Co1−xMnxFe2O4 (0≤x≤0.5) spinel ferrite thin films

The Co_1−xMn_xFe₂O₄ (0≤x≤0.5) spinel ferrite thin films were deposited on quartz substrates by chemical spray pyrolysis technique. The effect of Mn substitution on to the structural, electrical, dielectric and NO₂ gas sensing properties of cobalt ferrite thin films was studied. The X-ray diffraction analysis reveals that deposited films exhibit spinel cubic crystal structure. The lattice constant increases with the increase in Mn²⁺ content. The decrease in resistivity with increase in temperature suggests that the films have a semiconducting nature. The room temperature dielectric properties such as dielectric constant (ε′), loss tangent (tanδ), dielectric loss (ε′′) and AC conductivity have been studied in the frequency range 20 Hz–1 MHz. The film shows the highest sensor response at moderately low (150 °C) operating temperature. The effect of operating temperature, gas concentration, film selectivity and substitution of Mn on to gas response is carefully studied. The manganese substituted cobalt ferrite films are extremely selective towards NO₂ with a 20 times gas response compared with other gases. The gas response achieved nearly 92% of its initial value after 150 days, indicating good stability of the films.     

Thermal and optical properties of hyperbranched fluorinated polyimide/mesoporous SiO2 nanocomposites exhibiting high transparency and reduced thermo-optical coefficients

A series of hyper-branched polyimide (HBPI)/mesoporous SiO₂ nanocomposite films were prepared from a fluorinated anhydride (6FDA), a fluorinated triamine (TFAPOB), and mesoporous SiO₂ nanoparticles (NPs). The anhydride-terminated precursor of HBPI was functionalized using a coupling agent prior to mixing with SiO₂ NPs. The morphologies and thermal-optical properties of the nanocomposite films were investigated, with particular focus on their optical transparency, refractive indices (n), and thermo-optical (TO) coefficients. The absolute values of TO coefficients (|dn/dT|) of HBPI film (50.8 ppm/K) were significantly reduced to 13.4 ppm/K by homogeneous dispersion of 15 wt% of SiO₂ NPs. The HBPI/SiO₂ composite films exhibited high thermal stability without significant weight loss of up to 400 °C in air. The films also exhibited small coefficients of linear thermal expansion (CTEs) within the range 30–40 ppm/K. In addition, enhanced interfacial interactions between SiO₂ and HBPI significantly improve the optical transparency with cutoff wavelengths shorter than 450 nm. The refractive indices of HBPI/SiO₂ composite films were found to range from 1.477 to 1.502, which agrees well with the calculated values. This study shows that the incorporation of SiO₂ NPs in multi-functional HBPI matrix is a promising approach to prepare high performance thermally stable films for thermo-optic applications.     

Novel P(VDF-HFP)/BST nanocomposite films with enhanced dielectric properties and optimized energy storage performance

Nanocomposites using poly (vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), as the matrix, and barium strontium titanium oxide (BST) nanoparticles as the filler were systematically studied. P(VDF-HFP)/BST composite films containing different amounts of BST were prepared using the solution-casting method. The dielectric constant (ε_r), dielectric loss (tan δ), and their frequency and temperature dependence, were characterised for the films under weak electric fields. The behaviour of the films under high electric fields was explored using polarisation-electric field (P-E) loops. The ε_r was found to increase from 14.1 to 42.1 as the BST content increased from 0 vol% to 40 vol%, and the Maxwell-Wagner model showed a good fit with the measured ε_r values, indicating that the microstructure of the fabricated nanocomposites is uniform, which can also be observed in SEM images of all P(VDF-HFP)/BST nanocomposite films. In determining the temperature (T) dependence of the ε_r and tan δ of the composites, P(VDF-HFP) plays a decisive role, while BST plays an influential role. As the BST content increases, the charge/discharge energy density (U_charge/U_discharge) increases, while the breakdown strength (E_b) and charge-discharge efficiency (η) decrease. Notably, the maximal U_discharge 3.79 J/cm³ was obtained when the BST content was 20 vol% at 2100 kV/cm. In addition, from the perspective of practical application, when the applied electric field intensity is lower than 900 kV/cm or between 900 kV/cm and 2100 kV/cm, in order to obtain the maximal U_discharge, the P(VDF-HFP)/BST composite with BST content of 30 vol% or 20 vol% should be selected respectively.     

Microstructure and properties of polyimide/poly(vinylsilsesquioxane) hybrid composite films

Polyimide (PI)/poly(vinylsilsesquioxane) (PVSSQ) (PI/PVSSQ) hybrid composite films were prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)-4,4′-oxydianiline (ODA) polyamic acid and triethoxyvinylsilane (TEVS or VSSQ) via sol-gel process and thermal imidization. The presence of the PVSSQ showed a remarkable effect on the microstructure and properties of the polyimide based hybrid films. The transparency of the hybrid films decreased with increasing the content of the PVSSQ. The compatibility and interfacial interaction of the hybrid composites were evaluated by scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. The PI/PVSSQ hybrids showed nanocomposite formation when the contents of PVSSQ was less than 20 wt%. It was found that the surface topography was influenced by the composition of the PVSSQ. Incorporating of the PVSSQ increased the thermal stability and T_g of hybrid composites. The dielectric constant of the hybrid composites was reduced by adding PVSSQ up to a certain content, showed a minimum and then found to be increased. The dielectric constant values of the hybrid composites ranged from 2.59 to 3.78. The presence of the PVSSQ also showed significant effects on the mechanical properties of the polyimide films.     

Effect of the excess of bismuth on the morphology and properties of the BaBi2Nb2O9 thin films

In this study, the effect of bismuth content on the crystal structure, morphology and electric properties of barium bismuth niobate (BaBi₂Nb₂O₉) thin films was explored with the aid of X-ray diffraction (XRD), scanning electron microcopy (SEM), atomic force microscopy (AFM) and dielectric properties. BaBi₂Nb₂O₉ (BBN) thin films have been successfully prepared by the polymeric precursor methods and deposited by spin coating on Pt/Ti/SiO₂/Si (1 0 0) substrates. The phase formation, the grain size and morphology of the thin films were influenced by the addition of bismuth in excess. It was observed that the formation of single phase BBN for films was prepared with excess of bismuth up to 2 wt%. The films prepared with excess of the bismuth showed higher grain size and better dielectric properties. The 2 wt% bismuth excess BBN thin film exhibited dielectric constant of about 335 with a loss of 0.049 at a frequency of 100 kHz at room temperature.     

Dielectric properties of epoxy composites with modified multiwalled carbon nanotubes

We report here a high dielectric percolative polymer nanocomposite, fabricated by a combination of triethylene-tetramine (TETA) modified multiwalled carbon nanotube (named as TETA-MWNT) within epoxy resin matrix. In this composite system, with various TETA-MWNT volume fractions, the dielectric constant (K) is well fitted by the scaling law of the percolation theory with the percolation threshold f _c is 0.042 and the critical exponent p is 0.786. At 1,000 Hz of room temperature, the value of the dielectric constant is as high as 421 with the TETA-MWNT content of 4.14vol%, which is almost 60 times higher than that of epoxy resin. In contrast, a simple blend of pristine MWNT in epoxy composite shows evident lower dielectric constant and much higher loss with the same volume fraction.     

Characteristics of polyimide/barium titanate composite films

In this study, the characteristics of the polyimide/BaTiO₃ composite films with various amounts of BaTiO₃ were evaluated. Modifier 1-methoxy-2-propyl acetate was added during composite preparation to disperse the BaTiO₃ particles in polyimide matrix. Conversion of polyamic acid (PAA) to polyimide was not completed for the composite film with a high BaTiO₃ loading (90 wt%). Dielectric constant of the film increases from 3.53 to 46.50, at the sweep frequency of 10 kHz, as the BaTiO₃ content increases from 0 to 90 wt% (0–67.5 vol.%), which is mainly due to the relatively high dielectric constant of BaTiO₃ particles in the polyimide matrix. The dielectric losses at 10 kHz is ranging from 0.005 to 0.015, which is due to the switching of the domain wall. Water absorption decreases considerably with increasing BaTiO₃ content. With 10 wt% (2.5 vol.%) BaTiO₃ addition, the water absorption of the composite film reduces 45% from that of pure polyimide. Also, high loading of BaTiO₃ is not beneficial to reduce the water absorption of the composite film.     

Nano ZrO2 reinforced cellulose incorporated polyethylmethacrylate/polyvinyl alcohol composite films as semiconducting packaging materials

A simple in situ polymerization process is used to synthesize nanocomposite films with incorporation of cellulose and nano ZrO₂ (PEMA/PVA-C@ZrO₂). The change in structural, morphological, and functional properties are noticed due to combine effect of cellulose and zirconia which is studied by FTIR, XRD, XPS, FESEM, HRTEM, DLS, and AFM. The distribution of particle in the film is determined from dynamic light scattering (DLS). It is found that, dielectric permittivity is increased with percolation at 3 wt% of the nano ZrO₂. Further, the dielectric permittivity (ε') value is found to be 110 at 1 Hz with a low dielectric loss (Tan δ = 1.74) and an optimum dielectric permittivity is 172 at 1 Hz for 4 wt% loading of nano ZrO₂. Mechanical and thermal characteristics of the as-synthesized films are improved due to interfacial adhesion between zirconia and polymeric matrix. The chemical resistance, biodegradable characteristics, and refractive index of the nanocomposite films are also measured. It is noticed that, the barrier properties are increased by 20-folds due to the synergistic combination of nano ZrO₂ and cellulose with polymeric matrix. The enhancement in barrier properties with improved dielectric permittivity can enable the as-synthesized films for semiconducting packaging applications.     

Optical properties and new carbon forms of sputtered amorphous carbon films

Amorphous carbon films were deposited by r.f. magnetron sputtering at various bias voltages V_b applied on Si substrate. We studied the optical properties of the films using in situ spectroscopic ellipsometry (SE) measurements in the energy region 1.5–5.5 eV. From the SE data analysis the dielectric function ε(ω) of the a-C films was obtained, providing information about the electronic structure and the bonding configuration of a-C films. Based on the SE data the films are classified in three categories. In Category I and II belong the films developed with V_b≥0 V (rich in sp² bonds) and −100≤V_b<0 V (rich in sp³ bonds), respectively. The dielectric function of the films belonging in these two categories can be described with two Lorentz oscillators located in the energy range 2.5–5 eV (π–π^*) and 9–12 eV (σ–σ^*). A correlation was found between the oscillator strength and the sp² and sp³ contents. The latter were calculated by analyzing the ε(ω) with the Bruggeman effective medium theory. In films deposited with V_b<−100 V (Category III), the formation of a new and dense carbon phase was detected which exhibits a semi-metallic optical behavior and the ε(ω) can be described with two oscillators located at ∼1.2 and ∼5.5 eV.     

Electrical properties of poly(vinyl alcohol) (PVA) based on LiFePO<Subscript>4</Subscript> complex polymer electrolyte films

Li ion conducting polymer electrolyte films were prepared based on poly(vinyl alcohol) (PVA) with 5, 10, 15, 20, 25 and 30 wt% lithium iron phosphate (LiFePO₄) salt using a solution-casting technique. X-ray diffraction (XRD) was used to determine the complexation of the polymer with LiFePO₄ salt. Differential scanning (DSC) calorimetry was used to determine the melting temperatures of the pure PVA and complexed films. The maximum ionic conductivity was found to be 1.18 × 10⁻⁵ S cm⁻¹ for (PVA:LiFePO₄) (75:25) film, which increased to 3.12 × 10⁻⁵ S cm⁻¹ upon the addition of propylene carbonate (PC) plasticizer at ambient temperature. The Li⁺ ion transport number was found to be 0.40 for (PVA: LiFePO₄) (75:25) film using AC impedance and DC polarization methods. Dielectric studies were performed for these polymer electrolyte films in the frequency range of 10 Hz to 10 MHz at different temperatures. The activation energies of the complexed films were calculated from the dielectric loss tangent spectra and were found to be 0.35, 0.30, 0.27 and 0.28 eV. The cyclic voltammogram (CV) curves of (PVA: LiFePO₄) (75:25)+PC film exhibited higher specific capacities than those for other films.     

Effect of BN content on the structural,mechanical, and dielectric properties of PDCs-SiCN(BN) composite ceramics

Hexagonal boron nitride (h-BN) with low dielectric loss and high temperature resistance opens up new opportunities for the preparation of polymer-derived SiCN ceramics (PDCs-SiCN ceramics) with excellent mechanical and dielectric properties. BN-containing polymer-derived SiCN composite ceramics (PDCs-SiCN(BN) composite ceramics) with different BN content were prepared via a pyrolysis process of ball-milling-blended Polyvinylsilazane/boron nitride (PVSZ/BN) precursors. BN is stably embedded in the SiCN tissue and tightly bound with it. The appropriate content of BN greatly improves the mechanical properties of PDCs-SiCN ceramics, as BN reduces the number of pores and prevents crack expansion. Additionally, BN is also beneficial in lowering the dielectric loss of PDCs-SiCN ceramics because of the weakened polarization relaxation behavior. PDCs-SiCN (BN) composite ceramics have optimal mechanical and dielectric properties when the BN content is 1 wt%. The flexural strength, flexural modulus and compression strength of PDCs-SiCN(BN) composite ceramics with 1 wt% BN doping content were 189.37 MPa, 46.38 GPa, and 399.02 MPa, respectively. Its average dielectric loss (tanδ_ε) at 12.4-18 GHz is 0.0049.     

Low-frequency plasmonic state and tunable negative permittivity in percolative graphite / barium titanate composites

Percolative composites with negative permittivity have attracted widespread attentions due to their great potential in electromagnetic shielding and microwave devices. Targeting at achieving epsilon-negative properties, the percolative graphite/barium titanate (GR/BaTiO₃) composite is herein designed and prepared using hot-pressing sintered process. It's found that the plasma oscillations of delocalized electrons result in the epsilon negative permittivity behaviors when the GR contents exceeds the 2 wt% (percolation threshold), and frequency dependence of the negative permittivity which is in well agreement with the Drude model. Meanwhile, it's demonstrated that the ac conductivity represents a typical metal-like behavior as the conductive networks formed within the composites by the increasing GR loadings. Moreover, the equivalent circuit analysis reveals the relationships between capacitive-inductive transition and the conversion of permittivity changing from positive to negative. This work provides effective possibility for developing excellent dielectric properties of percolative GR/BaTiO₃ composite for capacitors and coil-less electrical inductors applications.     

Novel Al2Mo3O12-PTFE composites for microwave dielectric substrates

Nowadays, microwave dielectric substrate materials have been extensively investigated to meet the requirements of rapid development in modern communications. Among them, the composites of ceramic powder filled polytetrafluoroethylene (PTFE) have been a hot topic. However, the compatibility and connectivity between the surface of ceramics and PTFE molecular chains in the samples are usually low. Herein novel PTFE based composites with different contents of Al₂Mo₃O₁₂ (20–60 wt%) modified by C₁₄H₁₉F₁₃O₃Si (F8261) coupling agent were designed and prepared. The coupling agent F8261 has been successfully grafted to the surface of Al₂Mo₃O₁₂ powders, effectively promoting the densification and dielectric properties of the composites. As the content of the modified Al₂Mo₃O₁₂ powders increases from 20 to 60 wt%, the ε_r value increases from 3.4 to 4.2, and tanδ almost remains constant at the beginning and increases with much more Al₂Mo₃O₁₂ added. The Al₂Mo₃O₁₂-PTFE composites filled with 30 wt% Al₂Mo₃O₁₂ present the optimal dielectric properties of ε_r = 3.6 and tanδ = 0.0018 with a high density of 95.6%. In addition, the electromagnetic and multiphysic simulation of a 24 GHz substrate integrated waveguide filter on the basis of the 30 wt% Al₂Mo₃O₁₂ - 70 wt% PTFE composite was carried out. It was revealed that the filter presented high stability on the electrical parameters caused by self-heating and dimension deformation due to the good microwave dielectric, thermal and mechanical properties of the substrate. These results indicate that the as-prepared 30 wt% Al₂Mo₃O₁₂ - 70 wt% PTFE composite would be a promising candidate for high-performance microwave dielectric substrates.