A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this stud...A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.展开更多
Dielectric ceramics are promising in large-scale commercial millimeter-wave communication technology,such as 5G and the upcoming 6G,thanks to their excellent frequency selection characteristics and environmental stabi...Dielectric ceramics are promising in large-scale commercial millimeter-wave communication technology,such as 5G and the upcoming 6G,thanks to their excellent frequency selection characteristics and environmental stability.In this work,various contents of SbeO bonds were introduced into the MgTa_(2)O_(6)lattice using the solid-phase reaction method to investigate the effects on the lattice and microwave dielectric properties.XRD confirms that Sb ions successfully occupy Ta sites in the lattice and cause lattice shrinkage and crystallinity deterioration,which leads to a slight decrease in the quality factor.Furthermore,DFT calculations reveal that the doping leads to electron-biased aggregation toward O atoms,causing higher SbeO ionicity,but also attenuates the degree of ionization of Ta and Mg ions,which makes the dielectric constant of the doped samples vary non-monotonically with gradient doping.Satisfactorily,Sb doping substantially enhanced the thermal stability of the ceramics,with TCF values reduced from 36×10^(-6)℃^(-1)to 15×10^(-6)℃^(-1).展开更多
Ba_(1-x)Sr_(x)CuSi_(2)O_(6) 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 B...Ba_(1-x)Sr_(x)CuSi_(2)O_(6) 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 Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were investigated.Single BaCuSi_(2)O_(6) phase can be obtained when calcined at 1050℃ for 3 h or 950℃ for 10 h.The substitution of Ba^(2+) by Sr^(2+) can effectively promote the sintering process and the maximum solubility of Ba_(1-x)Sr_(x)CuSi_(2)O_(6) 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(Σχ^(μ))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 Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were achieved at x=0.20 when sintered at 1000℃ for 3 h:ε_(r)=8.25,Q×f=47616 GHz and τf=9.6 ppm/℃.展开更多
In recent years, interest in hydrogen as a fuel has sharply increased in the field of alternative and green energy due to its high energy capability and zero-emission behaviour. As a result, research in the developmen...In recent years, interest in hydrogen as a fuel has sharply increased in the field of alternative and green energy due to its high energy capability and zero-emission behaviour. As a result, research in the development of new highly efficient methods for producing high-purity hydrogen is relevant. This paper presents, for the first time, the test results of an electrochemical cell with a proton-conducting La_(0.9)Sr_(0.1)ScO_(3-δ) electrolyte and symmetrical Sr_(1.95)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)+ La_(0.9)Sr_(0.1)Sc_(0.9)Co_(0.1)O_(3-δ) electrodes as a hybrid setup for electricity generation in proton ceramic fuel cell mode, for hydrogen separation from H_(2)+ Ar mixture and the production of high-purity hydrogen from methane with simultaneous CO_(2) utilization.It was found that this electrochemical cell generates high flow rates of hydrogen during its separation through a proton-conducting membrane from H_(2)+ Ar mixture, about 500 cm^(3)h^(-1)cm^(-2)at a current density of 0.6 A cm^(-2)as well as about 370 cm^(3) h^(-1)cm^(-2)at a current density of 0.5 A cm^(-2) from CH_(4)+ CO_(2) mixture at 800 ℃ which shows that these cells are promising for hydrogen production.展开更多
基金This study is supported by the National Key Research and Development Program of China(No.2022YFB2807405)the Qinchuangyuan Citing High-level Innovation and Entrepreneurship Talent Projects(No.QCYRCXM-2022-40)+2 种基金the National Natural Science Foundation of China(Nos.U2341263 and 62371366)Open project of Yunnan Precious Metals Laboratory Co.,Ltd(No.YPML-2023050246)Innovation Capability Support Program of Shaanxi,China(Nos.2023-CX-PT-30 and 2022TD-28).
文摘A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.
基金National Key Scientific Instrument and Equipment Development Project(No.51827802)National Natural Science Foundation of China(No.51902042).
文摘Dielectric ceramics are promising in large-scale commercial millimeter-wave communication technology,such as 5G and the upcoming 6G,thanks to their excellent frequency selection characteristics and environmental stability.In this work,various contents of SbeO bonds were introduced into the MgTa_(2)O_(6)lattice using the solid-phase reaction method to investigate the effects on the lattice and microwave dielectric properties.XRD confirms that Sb ions successfully occupy Ta sites in the lattice and cause lattice shrinkage and crystallinity deterioration,which leads to a slight decrease in the quality factor.Furthermore,DFT calculations reveal that the doping leads to electron-biased aggregation toward O atoms,causing higher SbeO ionicity,but also attenuates the degree of ionization of Ta and Mg ions,which makes the dielectric constant of the doped samples vary non-monotonically with gradient doping.Satisfactorily,Sb doping substantially enhanced the thermal stability of the ceramics,with TCF values reduced from 36×10^(-6)℃^(-1)to 15×10^(-6)℃^(-1).
基金supported by the National Natural Science Foundation of China(NSFC-51572093,51772107 and 61771215)Research Project of Electronic Components and Devices of China(1807WM0004)the Major Programs of Technical Innovation in Hubei Province of China(2018AAA039).
文摘Ba_(1-x)Sr_(x)CuSi_(2)O_(6) 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 Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were investigated.Single BaCuSi_(2)O_(6) phase can be obtained when calcined at 1050℃ for 3 h or 950℃ for 10 h.The substitution of Ba^(2+) by Sr^(2+) can effectively promote the sintering process and the maximum solubility of Ba_(1-x)Sr_(x)CuSi_(2)O_(6) 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(Σχ^(μ))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 Ba_(1-x)Sr_(x)CuSi_(2)O_(6) were achieved at x=0.20 when sintered at 1000℃ for 3 h:ε_(r)=8.25,Q×f=47616 GHz and τf=9.6 ppm/℃.
文摘In recent years, interest in hydrogen as a fuel has sharply increased in the field of alternative and green energy due to its high energy capability and zero-emission behaviour. As a result, research in the development of new highly efficient methods for producing high-purity hydrogen is relevant. This paper presents, for the first time, the test results of an electrochemical cell with a proton-conducting La_(0.9)Sr_(0.1)ScO_(3-δ) electrolyte and symmetrical Sr_(1.95)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)+ La_(0.9)Sr_(0.1)Sc_(0.9)Co_(0.1)O_(3-δ) electrodes as a hybrid setup for electricity generation in proton ceramic fuel cell mode, for hydrogen separation from H_(2)+ Ar mixture and the production of high-purity hydrogen from methane with simultaneous CO_(2) utilization.It was found that this electrochemical cell generates high flow rates of hydrogen during its separation through a proton-conducting membrane from H_(2)+ Ar mixture, about 500 cm^(3)h^(-1)cm^(-2)at a current density of 0.6 A cm^(-2)as well as about 370 cm^(3) h^(-1)cm^(-2)at a current density of 0.5 A cm^(-2) from CH_(4)+ CO_(2) mixture at 800 ℃ which shows that these cells are promising for hydrogen production.
