Microwave dielectric ceramics(MWDCs)with a high Q×f value can improve the performance of radio frequency components like resonators,filters,antennas and so on.However,the quantitative structureproperty relationsh...Microwave dielectric ceramics(MWDCs)with a high Q×f value can improve the performance of radio frequency components like resonators,filters,antennas and so on.However,the quantitative structureproperty relationship(QSPR)for the Q×f value is complicated and unclear.In this study,machine learning methods were used to explore the QSPR and build up Q×f value prediction model based on a dataset of 164 ABO_(4)-type MWDCs.We employed five commonly-used algorithms for modeling,and 35 structural features having correlations with Q×f value were used as input.In order to describe structure from both global and local perspectives,three different feature construction methods were compared.The optimal model based on support vector regression with radial basis function kernel shows good performances and generalization capability.The features contained in the optimal model are primitive cell volume,molecular dielectric polarizability and electronegativity with A-and B-site mean method.The relationships between property and structure were discussed.The model used for the Q×f value prediction of tetragonal scheelite shows excellent performances(R^(2)=0.8115 and RMSE=8362.73 GHz),but it needs auxiliary features of average bond length,theoretical density and polarizability per unit volume for monoclinic wolframite ceramics to improve model prediction ability.展开更多
In present study,high-entropy(Mg_(1/2)Zn_(1/2))_(0.4+x)Li_(0.4)(Co_(1/2)Ni_(1/2))_(0.4-x)Al_(2)O_(4)ceramics were fabricated via the solid-state reaction approach.The high-entropy ceramics exhibited a spinel structure...In present study,high-entropy(Mg_(1/2)Zn_(1/2))_(0.4+x)Li_(0.4)(Co_(1/2)Ni_(1/2))_(0.4-x)Al_(2)O_(4)ceramics were fabricated via the solid-state reaction approach.The high-entropy ceramics exhibited a spinel structure with short-range local disorder and long-range structural order.The reduction of Co^(2+)and Ni^(2+)content suppress the damping behavior of atomic vibrations,promoting the structural ordering and contributing to higher quality factor(Q×f).The x=0.35 sample with sintering at 1550℃exhibited great microwave dielectric properties:a low dielectric constant(εr)of 7.92,a high-quality factor of 135,525 GHz,and a temperature coefficient of resonance frequency(Tf)of-49×10^(-6)℃^(-1).The_(εΓ)value was jointly dominated by both polarizability and relative density.The Q×f value was primarily connected to relative density,atomic vibrations,and the degree of covalency.The_(εГ)value was highly associated with the bond strength.Thesefindings demonstrate the effectiveness of adopting high-entropy composition design for significantly improving microwave dielectric properties.展开更多
The effects of different x values on the dielectric properties in the Ba6-3xSm8+2xTi18O54 microwave dielectric ceramics(0.3≤x≤0.7) were studied. The results showed that the major crystal phase was BaSm2Ti4O12 and th...The effects of different x values on the dielectric properties in the Ba6-3xSm8+2xTi18O54 microwave dielectric ceramics(0.3≤x≤0.7) were studied. The results showed that the major crystal phase was BaSm2Ti4O12 and the sintering temperature of the ceramics was 1340 ℃ when the x value was 0.67. The dielectric properties were better: εr≈79, tanδ≈1×10-4(1 MHz); εr≈80, Q·f=9230 GHz(3.97 GHz), τf=-17 ppm·℃-1.展开更多
With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid atten...With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation.In order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction method.The single columbite phase and dense structure are observed throughout the entire composition range.All elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron spectroscopy.Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman vibration.In addition,theɛr depends on the polarizability reflected by the C–M equation and Raman shift.Theτf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal structure.Moreover,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the conductance.Excellent microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×f.This work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.展开更多
基金the Postdoctoral Fellowship Program of China Postdoctoral Science Fund(GZC20232825)the Outstanding Academic/Technical Leader Project in Shanghai Plan of Action on Science and Technology Innovation(23XD1404600).
文摘Microwave dielectric ceramics(MWDCs)with a high Q×f value can improve the performance of radio frequency components like resonators,filters,antennas and so on.However,the quantitative structureproperty relationship(QSPR)for the Q×f value is complicated and unclear.In this study,machine learning methods were used to explore the QSPR and build up Q×f value prediction model based on a dataset of 164 ABO_(4)-type MWDCs.We employed five commonly-used algorithms for modeling,and 35 structural features having correlations with Q×f value were used as input.In order to describe structure from both global and local perspectives,three different feature construction methods were compared.The optimal model based on support vector regression with radial basis function kernel shows good performances and generalization capability.The features contained in the optimal model are primitive cell volume,molecular dielectric polarizability and electronegativity with A-and B-site mean method.The relationships between property and structure were discussed.The model used for the Q×f value prediction of tetragonal scheelite shows excellent performances(R^(2)=0.8115 and RMSE=8362.73 GHz),but it needs auxiliary features of average bond length,theoretical density and polarizability per unit volume for monoclinic wolframite ceramics to improve model prediction ability.
基金the Sichuan Science and Technology Program(No.2023YFQ0082)Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(No.EFMD2022005Z)Chengdu Science and Technology Program(No.2023-GH02-00061-HZ).
文摘In present study,high-entropy(Mg_(1/2)Zn_(1/2))_(0.4+x)Li_(0.4)(Co_(1/2)Ni_(1/2))_(0.4-x)Al_(2)O_(4)ceramics were fabricated via the solid-state reaction approach.The high-entropy ceramics exhibited a spinel structure with short-range local disorder and long-range structural order.The reduction of Co^(2+)and Ni^(2+)content suppress the damping behavior of atomic vibrations,promoting the structural ordering and contributing to higher quality factor(Q×f).The x=0.35 sample with sintering at 1550℃exhibited great microwave dielectric properties:a low dielectric constant(εr)of 7.92,a high-quality factor of 135,525 GHz,and a temperature coefficient of resonance frequency(Tf)of-49×10^(-6)℃^(-1).The_(εΓ)value was jointly dominated by both polarizability and relative density.The Q×f value was primarily connected to relative density,atomic vibrations,and the degree of covalency.The_(εГ)value was highly associated with the bond strength.Thesefindings demonstrate the effectiveness of adopting high-entropy composition design for significantly improving microwave dielectric properties.
文摘The effects of different x values on the dielectric properties in the Ba6-3xSm8+2xTi18O54 microwave dielectric ceramics(0.3≤x≤0.7) were studied. The results showed that the major crystal phase was BaSm2Ti4O12 and the sintering temperature of the ceramics was 1340 ℃ when the x value was 0.67. The dielectric properties were better: εr≈79, tanδ≈1×10-4(1 MHz); εr≈80, Q·f=9230 GHz(3.97 GHz), τf=-17 ppm·℃-1.
基金supported by the National Natural Science Foundation of China(No.52172122).
文摘With the increasing frequency of wireless mobile communication,dielectric materials with higher Q×f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation.In order to improve the Q×f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties,Ta5+ion is introduced to design and fabricate MgNb_(2-x)Ta_(x)O_(6)(0≤x≤0.8)ceramics by the solid-state reaction method.The single columbite phase and dense structure are observed throughout the entire composition range.All elements(Mg,Nb,Ta,and O)can be detected by X-ray photoelectron spectroscopy.Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2)and Ag(3)modes located at∼905 cm−1 dominate the Raman vibration.In addition,theɛr depends on the polarizability reflected by the C–M equation and Raman shift.Theτf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of[Nb/TaO6].Notably,the crucial factors for the huge improvement of Q×f are clarified deeply,in terms of the lower internal strain,the reduced ordering-induced domain size,and the chemical bond valence closer to the ionic valence state,which promotes the stability of crystal structure.Moreover,the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies,thereby reducing the dielectric loss caused by the conductance.Excellent microwave properties(ɛr=19.2,Q×f=170,000 GHz,andτf=−55.6 ppm℃–1)are achieved in MgNb1.4Ta0.6O6 ceramic,specifically a nearly 40%increase in the Q×f.This work has enriched the theory associated with low dielectric loss and provided the MgNb_(1.4)Ta_(0.6)O_(6) ceramic with a pretty high-Q×f for the application in the design of the 5G/6G wireless communication devices.
