Pristine LiNi0.5Mn1.5O4and Na-doped Li0.95Na0.05Ni0.5Mn1.5O4cathode materials were synthesized by a simple solid-statemethod.The effects of Na+doping on the crystalline structure and electrochemical performance of LiN...Pristine LiNi0.5Mn1.5O4and Na-doped Li0.95Na0.05Ni0.5Mn1.5O4cathode materials were synthesized by a simple solid-statemethod.The effects of Na+doping on the crystalline structure and electrochemical performance of LiNi0.5Mn1.5O4cathode materialwere systematically investigated.The samples were characterized by XRD,SEM,FT-IR,CV,EIS and galvanostatic charge/dischargetests.It is found that both pristine and Na-doped samples exhibit secondary agglomerates composed of well-defined octahedralprimary particle,but Na+doping decreases the primary particle size to certain extent.Na+doping can effectively inhibit the formationof LixNi1-xO impurity phase,enhance the Ni/Mn disordering degree,decrease the charge-transfer resistance and accelerate the lithiumion diffusion,which are conductive to the rate capability.However,the doped Na+ions tend to occupy8a Li sites,which forces equalamounts of Li+ions to occupy16d octahedral sites,making the spinel framework less stable,therefore the cycling stability is notimproved obviously after Na+doping.展开更多
Er^(3+),Na^(+)co-doped CaF_(2) transparent ceramics with Er^(3+)dopant concentration of 3% and Na^(+) of 0%,0.5%,1.0%,1.5% and 2.0% were fabricated by the vacuum hot pressing method with 16 mm in diameter and 3 mm in ...Er^(3+),Na^(+)co-doped CaF_(2) transparent ceramics with Er^(3+)dopant concentration of 3% and Na^(+) of 0%,0.5%,1.0%,1.5% and 2.0% were fabricated by the vacuum hot pressing method with 16 mm in diameter and 3 mm in thickness.The average grain size of the obtained Er,Na∶CaF_(2) powders varied from 28 nm to 36 nm with the shape of sphere.The effects of Na^(+) doping on the transmittance,microstructure and spectral properties of Er^(3+)∶CaF_(2) transparent ceramics were investigated.The transmittance of all the obtained ceramic samples is above 84%in the wavelength of 1000 nm.The results show that after introducing Na^(+)into Er^(3+)∶CaF_(2) transparent ceramics,charge-neutralized Er^(3+)-Na^(+) structure formed which prevent Er^(3+) from clustering.The emission spectra of Er^(3+) in CaF_(2) transparent ceramics at around 1.5 and 2.7μm could be modulated by adjusting the concentration of Na^(+) and the near-infrared fluorescence lifetime at around 1.5μm increase with the increasing of Na^(+) concentration,reaching a maximum of 56.75 ms.展开更多
SrZn2(PO4)2:Sm3+ phosphor was synthesized by a high temperature solid-state reaction in atmosphere. SrZn2(PO4)2:Sm3+ phosphor is efficiently excited by ultraviolet(UV) and blue light, and the emission peaks are assign...SrZn2(PO4)2:Sm3+ phosphor was synthesized by a high temperature solid-state reaction in atmosphere. SrZn2(PO4)2:Sm3+ phosphor is efficiently excited by ultraviolet(UV) and blue light, and the emission peaks are assigned to the transitions of 4G5/2-6H5/2(563 nm), 4G5/2-6H7/2(597 nm and 605 nm) and 4G5/2-6H9/2(644 nm and 653 nm). The emission intensities of SrZn2(PO4)2:Sm3+ are influenced by Sm3+ concentration, and the concentration quenching effect of SrZn2(PO4)2:Sm3+ is also observed. When doping A+(A=Li, Na and K) ions, the emission intensity of SrZn2(PO4)2:Sm3+ can be obviously enhanced. The Commission Internationale de l'Eclairage(CIE) color coordinates of SrZn2(PO4)2:Sm3+ locate in the orange-red region. The results indicate that the phosphor has a potential application in white light emitting diodes(LEDs).展开更多
Tin sulfide (SnS) has analogous structural features to tin selenide (SnSe), but contains more abundant resources as compared with SnSe. SnS has elicited attention as a potential eco-friendly therm oelectric (TE) mater...Tin sulfide (SnS) has analogous structural features to tin selenide (SnSe), but contains more abundant resources as compared with SnSe. SnS has elicited attention as a potential eco-friendly therm oelectric (TE) material. However, the intrinsic carrier concentration of SnS is very low, thereby hindering the performance improvement of the material. This study proposes that the TE properties of polycrystalline Nadoped SnS (synthesized through an improved chemical coprecipitation) can be significantly enhanced. The maximum power factor (PF) of 362 μW m^-1K^-2 at 873 K was achieved, presenting a state-of-the-art value for the polycrystalline SnS. Considering the merits of the improved electrical properties and lower thermal conductivity of SnS, the highest ZT was up to 0.52 at 873 K even without intentional chemical doping. This study offers an effective approach for improving the PF to achieve high ZT in SnS. Hence, we expect that this new perspective can be extended to other dopants and broaden the scope of synthesis technology.展开更多
基金Project(E2015202356)supported by the Natural Science Foundation of Hebei Province,ChinaProject(2013009)supported by the Technology Innovation Foundation for Outstanding Youth of Hebei University,China
文摘Pristine LiNi0.5Mn1.5O4and Na-doped Li0.95Na0.05Ni0.5Mn1.5O4cathode materials were synthesized by a simple solid-statemethod.The effects of Na+doping on the crystalline structure and electrochemical performance of LiNi0.5Mn1.5O4cathode materialwere systematically investigated.The samples were characterized by XRD,SEM,FT-IR,CV,EIS and galvanostatic charge/dischargetests.It is found that both pristine and Na-doped samples exhibit secondary agglomerates composed of well-defined octahedralprimary particle,but Na+doping decreases the primary particle size to certain extent.Na+doping can effectively inhibit the formationof LixNi1-xO impurity phase,enhance the Ni/Mn disordering degree,decrease the charge-transfer resistance and accelerate the lithiumion diffusion,which are conductive to the rate capability.However,the doped Na+ions tend to occupy8a Li sites,which forces equalamounts of Li+ions to occupy16d octahedral sites,making the spinel framework less stable,therefore the cycling stability is notimproved obviously after Na+doping.
基金National Key R&D Program of China(2023YFB3507400)。
文摘Er^(3+),Na^(+)co-doped CaF_(2) transparent ceramics with Er^(3+)dopant concentration of 3% and Na^(+) of 0%,0.5%,1.0%,1.5% and 2.0% were fabricated by the vacuum hot pressing method with 16 mm in diameter and 3 mm in thickness.The average grain size of the obtained Er,Na∶CaF_(2) powders varied from 28 nm to 36 nm with the shape of sphere.The effects of Na^(+) doping on the transmittance,microstructure and spectral properties of Er^(3+)∶CaF_(2) transparent ceramics were investigated.The transmittance of all the obtained ceramic samples is above 84%in the wavelength of 1000 nm.The results show that after introducing Na^(+)into Er^(3+)∶CaF_(2) transparent ceramics,charge-neutralized Er^(3+)-Na^(+) structure formed which prevent Er^(3+) from clustering.The emission spectra of Er^(3+) in CaF_(2) transparent ceramics at around 1.5 and 2.7μm could be modulated by adjusting the concentration of Na^(+) and the near-infrared fluorescence lifetime at around 1.5μm increase with the increasing of Na^(+) concentration,reaching a maximum of 56.75 ms.
基金supported by the National Natural Science Foundation of China(No.50902042)the Natural Science Foundation of Hebei Province in China(Nos.A2014201035 and E2014201037)the Education Office Research Foundation of Hebei Province in China(Nos.ZD2014036 and QN2014085)
文摘SrZn2(PO4)2:Sm3+ phosphor was synthesized by a high temperature solid-state reaction in atmosphere. SrZn2(PO4)2:Sm3+ phosphor is efficiently excited by ultraviolet(UV) and blue light, and the emission peaks are assigned to the transitions of 4G5/2-6H5/2(563 nm), 4G5/2-6H7/2(597 nm and 605 nm) and 4G5/2-6H9/2(644 nm and 653 nm). The emission intensities of SrZn2(PO4)2:Sm3+ are influenced by Sm3+ concentration, and the concentration quenching effect of SrZn2(PO4)2:Sm3+ is also observed. When doping A+(A=Li, Na and K) ions, the emission intensity of SrZn2(PO4)2:Sm3+ can be obviously enhanced. The Commission Internationale de l'Eclairage(CIE) color coordinates of SrZn2(PO4)2:Sm3+ locate in the orange-red region. The results indicate that the phosphor has a potential application in white light emitting diodes(LEDs).
基金supported by the National Key R&D Program of China (2018YFB0703603)the Basic Science Center Project of National Natural Science Foundation of China (NSFC, 51788104)the NSFC (11474176)
文摘Tin sulfide (SnS) has analogous structural features to tin selenide (SnSe), but contains more abundant resources as compared with SnSe. SnS has elicited attention as a potential eco-friendly therm oelectric (TE) material. However, the intrinsic carrier concentration of SnS is very low, thereby hindering the performance improvement of the material. This study proposes that the TE properties of polycrystalline Nadoped SnS (synthesized through an improved chemical coprecipitation) can be significantly enhanced. The maximum power factor (PF) of 362 μW m^-1K^-2 at 873 K was achieved, presenting a state-of-the-art value for the polycrystalline SnS. Considering the merits of the improved electrical properties and lower thermal conductivity of SnS, the highest ZT was up to 0.52 at 873 K even without intentional chemical doping. This study offers an effective approach for improving the PF to achieve high ZT in SnS. Hence, we expect that this new perspective can be extended to other dopants and broaden the scope of synthesis technology.
