Microwave dielectric ceramics(MWDCs)with low dielectric constant and low dielectric loss are desired in contemporary society,where the communication frequency is developing to high frequency(sub-6G).Herein,Nd_(2)(Zr_(...Microwave dielectric ceramics(MWDCs)with low dielectric constant and low dielectric loss are desired in contemporary society,where the communication frequency is developing to high frequency(sub-6G).Herein,Nd_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(NZ_(1−x)T_(x)M,x=0.02-0.10)ceramics were prepared through a solid-phase process.According to X-ray diffraction(XRD)patterns,the ceramics could form a pure crystal structure with the R3c(167)space group.The internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius-Mossotti relationship,Shannon’s rule,and Phillips-van Vechten-Levine(P-V-L)theory.Furthermore,theoretical dielectric loss of the ceramics was measured and analyzed by a Fourier transform infrared(IR)radiation spectrometer.Notably,when x=0.08 and sintered at 700℃,optimal microwave dielectric properties of the ceramics were obtained,including a dielectric constant(ε_(r))=10.94,Q·f=82,525 GHz(at 9.62 GHz),and near-zero resonant frequency temperature coefficient(τ_(f))=−12.99 ppm/℃.This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti^(4+)on the microwave dielectric properties and chemical bond characteristics of Nd_(2)Zr_(3)(MoO_(4))_(9)(NZM),which laid a solid foundation for the development of rare-earth molybdate MWDC system.展开更多
Li(_(1+x))2MgTi3O8(0.0≤x≤0.10)ceramics with Li non-stoichiometric ratios were prepared by the solidstate reaction method to inhibit the volatilization of Li.The effects of the Li non-stoichiometric ratios on the sin...Li(_(1+x))2MgTi3O8(0.0≤x≤0.10)ceramics with Li non-stoichiometric ratios were prepared by the solidstate reaction method to inhibit the volatilization of Li.The effects of the Li non-stoichiometric ratios on the sintering behavior,crystal structure,microscopic morphology,Raman vibrations,electron density,and dielectric properties of Li(_(1+x))2MgTi3O8 ceramics were systematically investigated.The Li(1+0.06)_(2)MgTi_(3)O_(8)ceramics demonstrate the best dielectric properties withεr=26.33,Q×f=69435 GHz(@6.87 GHz,54%improvement),tf=2.95×10^(-6)℃^(-1).For the non-intrinsic factors,the high relative density(97.15%)and larger grain size(16.78 mm)allow the dielectric properties to be improved.As for the intrinsic factors,a reasonable excess of Li improves the bond ionicity of the MgdO bond,the lattice energy of the TidO bond,and the electron cloud density,thus optimizing the dielectric properties.Raman spectroscopy leads to the same result from the point of view of lattice vibrations.At the same time,the distortion of the polyhedra is also improved,so that tf also approaches 0.The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.展开更多
The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamica...The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamically stable.The bulk moduli and shear moduli show that Al_(3)Sc has better resistance to volume and shape changes than AI3 Lu.However,the calculated results show that Al_(3)Lu has better plasticity than Al_(3)Sc.The properties of structural stability and elastic moduli of the crystal containing four major types of point defects in L1_(2)-Al_(3)X(X=Sc and Lu)were calculated.The mechanical properties of point defects show that point defects cause L1_(2)-Al_(3)X lattice distortion and change the corresponding elastic constants.Point defects reduce the Young’s,shear and bulk moduli but have little effects on the crystal brittleness and toughness of Al_(3)Sc and Al_(3)Lu.Therefore,we have found that Lu addition into aluminum alloys is a very good replacement for expensive Sc addition when the L1_(2)structures are desired for nucleation or strengthening precipitates in aluminum alloys.展开更多
Dense microwave dielectric ceramics of Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al1/2Ta1/2)^(4+) on their mic...Dense microwave dielectric ceramics of Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al1/2Ta1/2)^(4+) on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr_(2)Zr_(3)(MoO_(4))_(9) structures, which belonged to the space group R3¯c. The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce_(2)[Zr_(0.94)(Al_(1/2)Ta_(1/2))_(0.06)]_(3)(MoO_(4))_(9) with a relative permittivity (ε_(r)) of 10.46, quality factor (Q × f) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_(f)) of −11.50 ppm/℃ were achieved at 850 ℃.展开更多
Pr_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(x=0.1-1.0)ceramics were prepared via a conventional solid-state method,the dependence of crystal structure and bond characteristics on microwave dielectric properties was invest...Pr_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(x=0.1-1.0)ceramics were prepared via a conventional solid-state method,the dependence of crystal structure and bond characteristics on microwave dielectric properties was investigated systemically.The X-ray diffraction patterns indicated that the single-phase Pr_(2)Zr_(3)(MoO_(4))_(9)structure was formed in all the specimens.As the Ti^(4+)content increased,the lattice volume gradually decreased,which was ascribed to the fact that the ionic radius of Ti^(4+)was smaller than that of Zr^(4+).Notably,outstanding microwave dielectric properties withεr of 10.73-16.35,Q·f values of 80,696-18,726 GHz and minorτ_(f) values−14.1-−2.6 ppm/℃were achieved in Pr_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)ceramics.Theε_(r) increased with the rising x values,which was associated with the increase ofα/Vm values.The decreasing Q·f was affected by the decline of lattice energy of[Zr/TiO_(6)]octahedral.Theτf value was dominated by[Zr/TiO_(6)]octahedral distortion,Mo-O bond energy,bond strength and B-site bond valence.Furthermore,infrared reflection spectra suggested that the properties were mainly caused by the absorption of phonon,and the dielectric loss could be further reduced by optimizing the experimental process.展开更多
The replacement of liquid organic electrolytes with solid-state electrolytes(SSEs)is a feasible way to solve the safety issues and improve the energy density of lithium batteries.Developing SSEs materials that can wel...The replacement of liquid organic electrolytes with solid-state electrolytes(SSEs)is a feasible way to solve the safety issues and improve the energy density of lithium batteries.Developing SSEs materials that can well match with high-voltage cathodes and lithium metal anode is quite significant to develop high-energy-density lithium batteries.Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)SSE with NASICON structure exhibits high ionic conductivity,low cost and superior air stability,which enable it as one of the most hopeful candidates for all-solidstate batteries(ASSBs).However,the high interfacial impedance between LATP and electrodes,and the severe interfacial side reactions with the lithium metal greatly limit its applications in ASSBs.This review introduces the crystal structure and ion transport mechanisms of LATP and summarizes the key factors affecting the ionic conductivity.The side reaction mechanisms of LATP with Li metal and the promising strategies for optimizing interfacial compatibility are reviewed.We also summarize the applications of LATP including as surface coatings of cathode particles,ion transport network additives and inorganic fillers of composite polymer electrolytes.At last,this review proposes the challenges and the future development directions of LATP in SSBs.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51972143 and 52272126)State Key Laboratory of New Ceramics and Fine Processing,Tsinghua University (No.KFZD202101).
文摘Microwave dielectric ceramics(MWDCs)with low dielectric constant and low dielectric loss are desired in contemporary society,where the communication frequency is developing to high frequency(sub-6G).Herein,Nd_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(NZ_(1−x)T_(x)M,x=0.02-0.10)ceramics were prepared through a solid-phase process.According to X-ray diffraction(XRD)patterns,the ceramics could form a pure crystal structure with the R3c(167)space group.The internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius-Mossotti relationship,Shannon’s rule,and Phillips-van Vechten-Levine(P-V-L)theory.Furthermore,theoretical dielectric loss of the ceramics was measured and analyzed by a Fourier transform infrared(IR)radiation spectrometer.Notably,when x=0.08 and sintered at 700℃,optimal microwave dielectric properties of the ceramics were obtained,including a dielectric constant(ε_(r))=10.94,Q·f=82,525 GHz(at 9.62 GHz),and near-zero resonant frequency temperature coefficient(τ_(f))=−12.99 ppm/℃.This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti^(4+)on the microwave dielectric properties and chemical bond characteristics of Nd_(2)Zr_(3)(MoO_(4))_(9)(NZM),which laid a solid foundation for the development of rare-earth molybdate MWDC system.
基金supported by the National Natural Science Foundation of China(Grant No.51902042)the National Key Scientific Instrument and Equipment Development Project(No.51827802)the Major Science and Technology Specific Projects of Sichuan Province(No.2019ZDZX0026).
文摘Li(_(1+x))2MgTi3O8(0.0≤x≤0.10)ceramics with Li non-stoichiometric ratios were prepared by the solidstate reaction method to inhibit the volatilization of Li.The effects of the Li non-stoichiometric ratios on the sintering behavior,crystal structure,microscopic morphology,Raman vibrations,electron density,and dielectric properties of Li(_(1+x))2MgTi3O8 ceramics were systematically investigated.The Li(1+0.06)_(2)MgTi_(3)O_(8)ceramics demonstrate the best dielectric properties withεr=26.33,Q×f=69435 GHz(@6.87 GHz,54%improvement),tf=2.95×10^(-6)℃^(-1).For the non-intrinsic factors,the high relative density(97.15%)and larger grain size(16.78 mm)allow the dielectric properties to be improved.As for the intrinsic factors,a reasonable excess of Li improves the bond ionicity of the MgdO bond,the lattice energy of the TidO bond,and the electron cloud density,thus optimizing the dielectric properties.Raman spectroscopy leads to the same result from the point of view of lattice vibrations.At the same time,the distortion of the polyhedra is also improved,so that tf also approaches 0.The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.
基金the Ministry of Industry and Information Technology of China(61409220124)。
文摘The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamically stable.The bulk moduli and shear moduli show that Al_(3)Sc has better resistance to volume and shape changes than AI3 Lu.However,the calculated results show that Al_(3)Lu has better plasticity than Al_(3)Sc.The properties of structural stability and elastic moduli of the crystal containing four major types of point defects in L1_(2)-Al_(3)X(X=Sc and Lu)were calculated.The mechanical properties of point defects show that point defects cause L1_(2)-Al_(3)X lattice distortion and change the corresponding elastic constants.Point defects reduce the Young’s,shear and bulk moduli but have little effects on the crystal brittleness and toughness of Al_(3)Sc and Al_(3)Lu.Therefore,we have found that Lu addition into aluminum alloys is a very good replacement for expensive Sc addition when the L1_(2)structures are desired for nucleation or strengthening precipitates in aluminum alloys.
基金This work was supported by Shandong Postdoctoral Innovative Talents Support Plan(No.SDBX2020010)the National Natural Science Foundation of China(No.U1806221)+2 种基金Shandong Provincial Natural Science Foundation(No.ZR2020KA003)the Project of“20 Items of University”of Jinan(No.2019GXRC017)This work was also supported by the National Natural Science Foundation of China(No.51972143).
文摘Dense microwave dielectric ceramics of Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al1/2Ta1/2)^(4+) on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr_(2)Zr_(3)(MoO_(4))_(9) structures, which belonged to the space group R3¯c. The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce_(2)[Zr_(0.94)(Al_(1/2)Ta_(1/2))_(0.06)]_(3)(MoO_(4))_(9) with a relative permittivity (ε_(r)) of 10.46, quality factor (Q × f) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_(f)) of −11.50 ppm/℃ were achieved at 850 ℃.
基金supported by the National Natural Science Foundation of China(No.51972143)supported by State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KFZD202101)。
文摘Pr_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)(x=0.1-1.0)ceramics were prepared via a conventional solid-state method,the dependence of crystal structure and bond characteristics on microwave dielectric properties was investigated systemically.The X-ray diffraction patterns indicated that the single-phase Pr_(2)Zr_(3)(MoO_(4))_(9)structure was formed in all the specimens.As the Ti^(4+)content increased,the lattice volume gradually decreased,which was ascribed to the fact that the ionic radius of Ti^(4+)was smaller than that of Zr^(4+).Notably,outstanding microwave dielectric properties withεr of 10.73-16.35,Q·f values of 80,696-18,726 GHz and minorτ_(f) values−14.1-−2.6 ppm/℃were achieved in Pr_(2)(Zr_(1−x)Ti_(x))_(3)(MoO_(4))_(9)ceramics.Theε_(r) increased with the rising x values,which was associated with the increase ofα/Vm values.The decreasing Q·f was affected by the decline of lattice energy of[Zr/TiO_(6)]octahedral.Theτf value was dominated by[Zr/TiO_(6)]octahedral distortion,Mo-O bond energy,bond strength and B-site bond valence.Furthermore,infrared reflection spectra suggested that the properties were mainly caused by the absorption of phonon,and the dielectric loss could be further reduced by optimizing the experimental process.
基金Key-Area Research and Development Program of Guangdong Province,Grant/Award Number:2020B090919001National Natural Science Foundation of China,Grant/Award Number:U2001220+1 种基金Shenzhen All-Solid-State Lithium Battery Electrolyte Engineering Research Center,Grant/Award Number:XMHT20200203006Shenzhen Technical Plan Project,Grant/Award Number:JCYJ20180508152210821,JCYJ20170817161221958,JCYJ20180508152135822。
文摘The replacement of liquid organic electrolytes with solid-state electrolytes(SSEs)is a feasible way to solve the safety issues and improve the energy density of lithium batteries.Developing SSEs materials that can well match with high-voltage cathodes and lithium metal anode is quite significant to develop high-energy-density lithium batteries.Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)SSE with NASICON structure exhibits high ionic conductivity,low cost and superior air stability,which enable it as one of the most hopeful candidates for all-solidstate batteries(ASSBs).However,the high interfacial impedance between LATP and electrodes,and the severe interfacial side reactions with the lithium metal greatly limit its applications in ASSBs.This review introduces the crystal structure and ion transport mechanisms of LATP and summarizes the key factors affecting the ionic conductivity.The side reaction mechanisms of LATP with Li metal and the promising strategies for optimizing interfacial compatibility are reviewed.We also summarize the applications of LATP including as surface coatings of cathode particles,ion transport network additives and inorganic fillers of composite polymer electrolytes.At last,this review proposes the challenges and the future development directions of LATP in SSBs.
