Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(...Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.展开更多
Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN fi...Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN films at low temperatures.When the NKN film was deposited on one SNO monolayer,the NKN memristor exhibited normal bipolar switching characteristics,which could be attributed to the formation and destruction of oxygen vacancy filaments.Moreover,the NKN memristor with one SNO monolayer exhibited artificial synaptic properties.However,the NKN memristor deposited on two SNO monolayers exhibited self-rectifying bipolar switching properties,with the two SNO monolayers acting as tunneling barriers in the memristor.The conduction mechanism of the NKN memristor with two SNO monolayers in the highresistance state is attributed to Schottky emission,direct tunneling,and Fowler–Nordheim(FN)tunneling.The current conduction in this memristor in the low-resistance state was governed by direct tunneling and FN tunneling.Additionally,the NKN memristor with two SNO monolayers exhibited large ON/OFF and rectification ratios and artificial synaptic properties.Therefore,an NKN memristor with two SNO monolayers can be used for fabricating artificial synaptic devices with a cross-point array structure.展开更多
Doping and substitution methods are predominantly employed in the synthesis of ceramics to achieve their desired functional properties.We studied the behavior of excessive dopants in addition to an existing stoichiome...Doping and substitution methods are predominantly employed in the synthesis of ceramics to achieve their desired functional properties.We studied the behavior of excessive dopants in addition to an existing stoichiometric composition using a high-throughput continuous compositional spread sputtering method.We paid attention to the possible formation of thermodynamically unstable phases by the addition of an excessive amount of dopants.We showed that even when dopants were added as an additive,they dissolved into the existing lattice due to the benefit of the entropy of mixing.Regardless of excessiveness,all added elements incorporated into the lattice,stabilized by the tolerance factor.We also demonstrated ourfindings exemplarily with lead iron niobate to induce magnetic properties alongside inherent ferroelectricity(M_(S)=10 emu/cm^(3),P_(S)=16μC/cm^(2)).We compare the results from CCS with those from the non-additive solid-state method,leading to a conclusion that the benefit from the entropy of mixing allows foreign elements to substitute for the elements initially residing in the lattice to a degree in compliance with the Goldschmidt tolerance factor.This observation was confirmed by a density functional theory calculation.We anticipate that our study could necessitate intensive research on achieving desired composition through industry-friendly processing.展开更多
A monolayer of Sr2Nb3Oio(SNO)is deposited on the Pt/Ti/SiCWSi(Pt?Si)or Pt/Ti/polyimide(Pt-Pl)substrate by using the Langmuir-Blodgett method and employed as a seed-layer for the growth of a crystalline(Nai_xKx)NbO3(NK...A monolayer of Sr2Nb3Oio(SNO)is deposited on the Pt/Ti/SiCWSi(Pt?Si)or Pt/Ti/polyimide(Pt-Pl)substrate by using the Langmuir-Blodgett method and employed as a seed-layer for the growth of a crystalline(Nai_xKx)NbO3(NKN)film at 350℃.The crystalline NKN film is grown along the[001]direction on the SNO/Pt-Si(or SNO/Pt-PI)substrate.Due to the presence of oxygen vacancies in the SNO seed-layer,the NKN film exhibits low ferroelectric properties and large leakage current.To ameliorate these properties,the SNO/Pt-Si substrate is annealed in a 50 Torr oxygen atmosphere at 300℃,which removes the oxygen vacancies.Consequently,the NKN film deposited on this substrate exhibits promising electrical properties,namely a dielectric constant of 278,dissipation factor of 1.7%,a piezoelectric 8nstant of 175 pm`V^-1,and a leakage current density of 6.47 x 10^-7 A cm^-2 at-0.2 MV crrT1.Similar electrical properties are obtained from the NKN film grown on the flexible SNO/Pt-PI substrate at 350°C.Hence,the NKN films grown on the SNO seed-layer at 350°C can be applied to electronic devices with flexible polymer substrates.展开更多
We present a facile method for producing superhydrophobic nanograss-coated （SNGC） glass surfaces that possess both reduced reflectivity and self-cleaning properties at the air/glass interface. The refractive index o...We present a facile method for producing superhydrophobic nanograss-coated （SNGC） glass surfaces that possess both reduced reflectivity and self-cleaning properties at the air/glass interface. The refractive index of a CaF2 nanograss （NG） layer on a glass substrate, deposited by glancing angle vapor deposition, is 1.04 at 500 nm, which is the second-lowest value ever reported so far. The fluorinated NG layer gives rise to a high water contact angle （〉150°） and very efficient cleaning out of dust with water drops. Using the dual functionalities of the SNGC glass, we demonstrate superhydrophobic and antireflective organic photovoltaic cells with excellent power conversion efficiency.展开更多
High power light-emitting diodes （LEDs） lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market a...High power light-emitting diodes （LEDs） lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market are price and light efficiency, respectively, and they are greatly influenced by the materials and design factors used in high power LED package. This article presents a new design and materials processing technology to realize the solution of LED packaging with advantageous in price and performance. Cost effective materials and processing technology can be realized via thick film glass-ceramic insulating layer and silver conductor. Highly effective thermal design using direct heat dissipation to heat sink in LED package is demonstrated.展开更多
0.96(K_(0.5)Na_(0.5-z)Li_(z))(Nb_(0.92)Sb_(0.08))O_(3)-0.04(Ca_(0.5)Sr_(0.5))ZrO_(3)[(KN_(0.5-z)L_(z))NS-CSZ]piezoceramics(0≤z≤0.04)were aligned in the[001]orientation using 3%(in mole)NaNbO_(3)templates with a larg...0.96(K_(0.5)Na_(0.5-z)Li_(z))(Nb_(0.92)Sb_(0.08))O_(3)-0.04(Ca_(0.5)Sr_(0.5))ZrO_(3)[(KN_(0.5-z)L_(z))NS-CSZ]piezoceramics(0≤z≤0.04)were aligned in the[001]orientation using 3%(in mole)NaNbO_(3)templates with a large Lotgering factor(>97%).Their crystal structures transformed from the orthorhombic-pseudocubic(O-P)structure to the orthorhombic-tetragonal-pseudocubic(O-T-P)structure with an increasing z.The P structure was interpreted as a rhombohedral R3m structure.The piezoelectricity of the compositions increased after[001]-texturing,and the enhancement was proportional to the O phase quantity.The composition(z=0.03)exhibited the highest piezoelectric constant(d_(33);670 pC/N)and electromechanical coupling factor(k_(p);0.56).Piezoelectric energy harvesters were produced using the untextured and textured samples(z=0.03).The textured harvester delivered a large power density of 26.6 mW/mm^(3),which was larger than that of the untextured harvester owing to the enhanced kp and d_(33)×g_(33) of the textured piezoceramic.A multilayer actuator was produced using the textured sample(z=0.03),and it exhibited a large acceleration(44.2 G)and displacement(±3,730 mm)at±25 V.Therefore,the[001]-textured(KN_(0.47)L_(0.03))NS-CSZ piezoceramic is suitable for piezoelectric energy harvesters and actuators.展开更多
基金supported by the Korea Institute of Science and Technology(KIST)Institutional Program(Project No.2E30212)the National Research Foundation of Korea(NRF)(NRF-2020M3H4A1A0308297811)。
文摘Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation properties.However,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2020R1A2B5B01002063)the KU-KIST Graduate School Program of the Korea University。
文摘Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN films at low temperatures.When the NKN film was deposited on one SNO monolayer,the NKN memristor exhibited normal bipolar switching characteristics,which could be attributed to the formation and destruction of oxygen vacancy filaments.Moreover,the NKN memristor with one SNO monolayer exhibited artificial synaptic properties.However,the NKN memristor deposited on two SNO monolayers exhibited self-rectifying bipolar switching properties,with the two SNO monolayers acting as tunneling barriers in the memristor.The conduction mechanism of the NKN memristor with two SNO monolayers in the highresistance state is attributed to Schottky emission,direct tunneling,and Fowler–Nordheim(FN)tunneling.The current conduction in this memristor in the low-resistance state was governed by direct tunneling and FN tunneling.Additionally,the NKN memristor with two SNO monolayers exhibited large ON/OFF and rectification ratios and artificial synaptic properties.Therefore,an NKN memristor with two SNO monolayers can be used for fabricating artificial synaptic devices with a cross-point array structure.
基金the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(2021-M1A3B2A01078712)This research was supported by the Korea Institute of Science and Technology Future Resource Program(2E33181)the National Research Foundation of Korea(NRF)grant by the Korea government(No.2021R1A2C2010695,RS-2023-00222719).
文摘Doping and substitution methods are predominantly employed in the synthesis of ceramics to achieve their desired functional properties.We studied the behavior of excessive dopants in addition to an existing stoichiometric composition using a high-throughput continuous compositional spread sputtering method.We paid attention to the possible formation of thermodynamically unstable phases by the addition of an excessive amount of dopants.We showed that even when dopants were added as an additive,they dissolved into the existing lattice due to the benefit of the entropy of mixing.Regardless of excessiveness,all added elements incorporated into the lattice,stabilized by the tolerance factor.We also demonstrated ourfindings exemplarily with lead iron niobate to induce magnetic properties alongside inherent ferroelectricity(M_(S)=10 emu/cm^(3),P_(S)=16μC/cm^(2)).We compare the results from CCS with those from the non-additive solid-state method,leading to a conclusion that the benefit from the entropy of mixing allows foreign elements to substitute for the elements initially residing in the lattice to a degree in compliance with the Goldschmidt tolerance factor.This observation was confirmed by a density functional theory calculation.We anticipate that our study could necessitate intensive research on achieving desired composition through industry-friendly processing.
文摘A monolayer of Sr2Nb3Oio(SNO)is deposited on the Pt/Ti/SiCWSi(Pt?Si)or Pt/Ti/polyimide(Pt-Pl)substrate by using the Langmuir-Blodgett method and employed as a seed-layer for the growth of a crystalline(Nai_xKx)NbO3(NKN)film at 350℃.The crystalline NKN film is grown along the[001]direction on the SNO/Pt-Si(or SNO/Pt-PI)substrate.Due to the presence of oxygen vacancies in the SNO seed-layer,the NKN film exhibits low ferroelectric properties and large leakage current.To ameliorate these properties,the SNO/Pt-Si substrate is annealed in a 50 Torr oxygen atmosphere at 300℃,which removes the oxygen vacancies.Consequently,the NKN film deposited on this substrate exhibits promising electrical properties,namely a dielectric constant of 278,dissipation factor of 1.7%,a piezoelectric 8nstant of 175 pm`V^-1,and a leakage current density of 6.47 x 10^-7 A cm^-2 at-0.2 MV crrT1.Similar electrical properties are obtained from the NKN film grown on the flexible SNO/Pt-PI substrate at 350°C.Hence,the NKN films grown on the SNO seed-layer at 350°C can be applied to electronic devices with flexible polymer substrates.
文摘We present a facile method for producing superhydrophobic nanograss-coated （SNGC） glass surfaces that possess both reduced reflectivity and self-cleaning properties at the air/glass interface. The refractive index of a CaF2 nanograss （NG） layer on a glass substrate, deposited by glancing angle vapor deposition, is 1.04 at 500 nm, which is the second-lowest value ever reported so far. The fluorinated NG layer gives rise to a high water contact angle （〉150°） and very efficient cleaning out of dust with water drops. Using the dual functionalities of the SNGC glass, we demonstrate superhydrophobic and antireflective organic photovoltaic cells with excellent power conversion efficiency.
文摘High power light-emitting diodes （LEDs） lighting has drawn a great interest in the field of street light system in recent years. Key parameters for successful launching of LED street light in the commercial market are price and light efficiency, respectively, and they are greatly influenced by the materials and design factors used in high power LED package. This article presents a new design and materials processing technology to realize the solution of LED packaging with advantageous in price and performance. Cost effective materials and processing technology can be realized via thick film glass-ceramic insulating layer and silver conductor. Highly effective thermal design using direct heat dissipation to heat sink in LED package is demonstrated.
基金supported by a National Research Foundation(NRF)of Korea grant funded by the Korean government(MSIT)(No.RS-2023-00254689).
文摘0.96(K_(0.5)Na_(0.5-z)Li_(z))(Nb_(0.92)Sb_(0.08))O_(3)-0.04(Ca_(0.5)Sr_(0.5))ZrO_(3)[(KN_(0.5-z)L_(z))NS-CSZ]piezoceramics(0≤z≤0.04)were aligned in the[001]orientation using 3%(in mole)NaNbO_(3)templates with a large Lotgering factor(>97%).Their crystal structures transformed from the orthorhombic-pseudocubic(O-P)structure to the orthorhombic-tetragonal-pseudocubic(O-T-P)structure with an increasing z.The P structure was interpreted as a rhombohedral R3m structure.The piezoelectricity of the compositions increased after[001]-texturing,and the enhancement was proportional to the O phase quantity.The composition(z=0.03)exhibited the highest piezoelectric constant(d_(33);670 pC/N)and electromechanical coupling factor(k_(p);0.56).Piezoelectric energy harvesters were produced using the untextured and textured samples(z=0.03).The textured harvester delivered a large power density of 26.6 mW/mm^(3),which was larger than that of the untextured harvester owing to the enhanced kp and d_(33)×g_(33) of the textured piezoceramic.A multilayer actuator was produced using the textured sample(z=0.03),and it exhibited a large acceleration(44.2 G)and displacement(±3,730 mm)at±25 V.Therefore,the[001]-textured(KN_(0.47)L_(0.03))NS-CSZ piezoceramic is suitable for piezoelectric energy harvesters and actuators.
