Structural Transition Behavior Research Articles

Size-dependent guest-memory switching of the flexible and robust adsorption characteristics of layered metal-organic frameworks.

Flexible-robust metal-organic frameworks (MOFs), which exhibit unique hybrid nature comprising both flexible and rigid framework characteristics, exhibit high potential for hydrocarbon separations. However, no clear guidelines have been established to regulate their hybrid characteristics owing to limited understanding of their adsorption mechanism. This study investigates the effects of the particle size of a flexible-robust MOF on its adsorption and structural transition behaviors. The robust nature originates from the structural transition of a metastable guest-free structure, while its flexible nature arises from another guest-free structure. The type of guest-free structure is predominantly determined by the particle size; particles below the critical size are trapped in the metastable guest-free structure. Notably, the critical size varies with the type of guest molecule to be removed; consequently, the difference in critical size results in guest-memory characteristics, enabling guest-free structure switching. These results underscore the importance of controlling the particle size to fine-tune hybrid adsorption characteristics of flexible-robust MOFs.

Ethane Triggered Gate‐Opening in a Flexible−Robust Metal−Organic Framework for Ultra‐high Purity Ethylene Purification

Priority recognition separation of inert and larger ethane molecules from high‐concentration ethylene mixtures instead of traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report the ethane triggered gate‐opening in the flexible‐robust metal−organic framework Zn(ad)(min), the 3‐methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross‐section well‐matched ethane molecule, thus achieving the unprecedent ethane adsorption capacity (62.6 cm3 g‐1) and ethane/ethylene uptake ratio (3.34) under low‐pressure region (0.1 bar and 298 K). The ethane‐induced structural transition behavior is uncovered by a collaboration of single‐crystal X‐ray diffraction, in‐situ variable pressure X‐ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross‐section matching and multiple supramolecular interactions within the tailor‐made pore channels. Dynamic breakthrough experiments revealed the outstanding separation performance of Zn(ad)(min) in the production of ultra‐high purity ethylene (> 99.995%) with a productivity of up to 39.2 L/kg under ambient conditions.

Ethane Triggered Gate-Opening in a Flexible-Robust Metal-Organic Framework for Ultra-high Purity Ethylene Purification.

Priority recognition separation of inert and larger ethane molecules from high-concentration ethylene mixtures instead of traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report the ethane triggered gate-opening in the flexible-robust metal-organic framework Zn(ad)(min), the 3-methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross-section well-matched ethane molecule, thus achieving the unprecedent ethane adsorption capacity (62.6cm3 g-1) and ethane/ethylene uptake ratio (3.34) under low-pressure region (0.1 bar and 298 K). The ethane-induced structural transition behavior is uncovered by a collaboration of single-crystal X-ray diffraction, in-situ variable pressure X-ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross-section matching and multiple supramolecular interactions within the tailor-made pore channels. Dynamic breakthrough experiments revealed the outstanding separation performance of Zn(ad)(min) in the production of ultra-high purity ethylene (> 99.995%) with a productivity of up to 39.2 L/kg under ambient conditions.

Ultrafast structural transition and electron-phonon/phonon–phonon coupling in antimony revealed by nonadiabatic molecular dynamics

Real-time time-dependent density-functional theory molecular dynamics (rt-TDDFT-MD) reveals the nonadiabatic dynamics of the ultrafast photoinduced structural transition in a typical phase-change material antimony (Sb) with Peierls distortion (PD). As the excitation intensity increases from 3.54% to 5.00%, three distinct structural transition behaviors within 1 ps are observed: no PD flipping, nonvolatile-like PD flipping, and nonstop back-and-forward PD flipping. Analyses on electron-phonon and phonon-phonon couplings indicate that the excitation-activated coherent A1gphonon mode by electron-phonon coupling drives the structural transition within several hundred femtoseconds. Then, the energy of coherent motions are transformed into that of random thermal motions via phonon-phonon coupling, which prevents the A1g-mode-like coherent structure oscillations. The electron-phonon coupling and coherent motions will be enhanced with increasing the excitation intensity. Therefore, a moderate excitation intensity that can balance the coherent and decoherent thermal movements will result in a nonvolatile-like PD flipping. These findings illustrate important roles of nonadiabatic electron-phonon/phonon-phonon couplings in the ultrafast laser-induced structural transitions in materials with PD, offering insights for manipulating their structures and properties by light.

Direct observation of ordered-disordered structural transition of MoS2-confined ionic liquids

Ionic liquids (ILs) are an emerging class of media of fundamental importance for chemical engineering, especially due to their interaction with solid surfaces. Here, we explore the growth phenomenon of surface-confined ILs and reveal a peculiar structural transition behavior from order to disorder above a threshold thickness. This behavior can be explained by the variation of interfacial forces with increasing distance from the solid surface. Direct structural observation of different ILs highlights the influence of the ionic structure on the growth process. Notably, the length of the alkyl chain in the cation is found to be a determining factor for the ordering trend. Also, the thermal stability of surface-confined ILs is investigated in depth by controlling annealing treatments. It is found that the ordered monolayer ILs exhibit high robustness against high temperatures. Our findings provide new perspectives on the properties of surface-confined ILs and open up potential avenues for manipulating the structures of nanometer-thick IL films for various applications.

Manganese substitution effect on physical properties of sol-gel derived DyFeO3 orthoferrite

A simple composite DyFe(1-x)MnxO3 (x = 0, 0.1, 0.3, 0.5) powders were successfully prepared by the sol–gel method. The effect of Mn modification on the structure, thermal and phase transition behaviour of DyFeO3 orthoferrite was investigated. Mn modification didn't show any structural change and all the samples confirmed the pure orthorhombic phase with Pbnm space group. However, a contradicting trend in the variation of lattice parameters were observed due to the presence of mixed oxidation state of Dy, Fe and Mn in the sample leading to oxygen vacancies. The presence of mixed oxidation state was confirmed through X-ray photoemission spectra (XPS). Scanning electron microscopy (SEM) and Williamson Hall (WH) plot confirmed a decrease in particle sizes with increasing Mn concentration leading to an increase in the specific surface area which suggested an inhibition of grain growth with Mn modification. The defects-initiated change in physical behaviour in terms of structural, thermal, microstructural and dielectric are analyzed and discussed in detail.

Influence of poly(methyl methacrylate) on the structure and phase transition behavior of poly(vinylidene fluoride)

The structure and organization of poly(vinylidene fluoride) (PVDF) spherulites in blends with poly(methyl methacrylate) of high (PMMA-H) and low (PMMA-L) molecular weights, respectively, have been studied in details. It is confirmed that the addition of PMMA-H and PMMA-L have different influence on the morphologies of PVDF spherulites in several aspects, such as the spacing of ring-band α-PVDF spherulites, the kinetics of both α-PVDF crystallization and α−γ′ solid phase transition, as well as the formation of Wagon-Wheel spherulites. First, incorporation of PMMA-L enlarges the band spacing, which is associated to the increased chain mobility of crystallizable PVDF that helps to release the surface stresses of lamellae. In contrast, the low mobility of PMMA-H chains enhances the congestion at fold surfaces, which results in a vigorous twisting and thus the formation of tightened ring-band α-PVDF structure. Second, the PMMA-H reduces the crystallization rate of PVDF more severely than the PMMA-L, resulting in an extremely slow growth rate of α-PVDF spherulites in PVDF/PMMA-H sample at 160 °C, only about one-twenty-third compared to the neat PVDF. Third, the remarkably reduced α-PVDF spherulite growth rate and enhanced α−γ′ transition rate at 160 °C lead to the formation of Wagon-Wheel PVDF spherulites with inner γ′-PVDF crystals and outer γ crystals. It originates from the synchronization of slow α-PVDF growth and accelerated α−γ′ transition rate through homoepitaxy. That is, when the α−γ′ transition with exceeded rate reaches the growth front of the original α-PVDF spherulite, the transformed γ′-PVDF crystals trigger the growth of γ-PVDF crystals directly from melt with non-band feature. These results help to unravel the formation mechanism of Wagon-Wheel PVDF spherulites to be the competition of α-γ′ crystal transformation and α-spherulite radial growth rates.

Influence of Bi3+ 6s2 lone pair hybridization on the La0.7Pb0.3-xBixMnO3 (x = 0–0.04) crystal structure and electro-magnetic phase transition behaviour

Current manuscript focuses on the variations in structural, electrical, and magnetic behaviour exhibited by the new perovskite compound of La0.7Pb0.3-xBixMnO3 (x = 0–0.04). The samples were synthesized using the conventional solid state preparation method. The sample structural properties were determined using X-ray diffraction (XRD), and the diffraction data was refined using Rietveld refinement techniques to determine the samples structural parameters. The XRD analysis shows that the x = 0–0.02 samples crystallized as a single-phase sample, whereas x = 0.04 indicates secondary phase formation of Mn3O4 impurities. Though, all the sample crystallized in a rhombohedral structure with a space group of R-3c. The tolerance factor of the sample was calculated to determine the distortion severity of the structure. Scanning electron microscope (SEM) was used to study the samples' morphological properties. Fourier transform infrared (FTIR) indicates absorption range within 450–600 cm−1 which corresponds with absorption range of Mn–O bond formation. Ultraviolet–visible spectroscopy (UV–Vis) analysis of the sample exhibited an optical energy bandgap within the range of 1.71 eV–2.16 eV. The samples exhibit a clear metal-insulator transition with various TMI values ranging from 256 K until 292 K. Conduction mechanisms at low temperatures (T < TMI) were suggested due to grain or domain boundaries, electron-electron, and electron–magnon mechanisms, while SPH analysis were done to determine the electron conductivity behaviour at high temperatures (T > TMI). The AC susceptibility and Vibrating-sample Magnetometer (VSM) were done to study the magnetic properties of the samples and confirm the transition from ferromagnetic (FM) to paramagnetic (PM) with variation of TC value from 298 K (x = 0) to 289 (x = 0.02) and 287 (x = 0.04).

Effect of alkali-metal cations on synthesis of stoichiometric layered perovskite oxynitrides

Layered perovskite oxynitrides, which contain a stoichiometric lattice N content, are promising visible-light-driven photocatalysts. However, their synthesis remains a challenge for inorganic chemists. Herein, we report the successful synthesis of layered perovskite oxynitrides A2A'2Ta3O9N with different cations at A/A′-sites (A = Na, K, Rb, Cs; A' = Ca, Sr, Ba) via thermal ammonolysis from layered Dion–Jacobson phase oxide precursors (AA'2Ta3O10). We present the first experimental study of layered oxynitride formation across the A and A′ cation size series, revealing that the A-site alkali-metal cation rather than the A′-site alkaline-earth metal cation is critical to the successful synthesis of the stoichiometric layered oxynitrides. Nitrided products with A = Na, K, or Rb exhibited structural transitions, while no structural transition was observed for Cs. Interestingly, nitrided products with A = Rb and K exhibited the same structural transition behavior, i.e., alkali-metal cations entered the interlayer to form an oxynitride with a composition A2A'2Ta3O9N·nH2O. By contrast, with A = Na, it formed an oxynitride that differs from the Ruddlesden–Popper structure but has the same composition of A2A'2Ta3O9N·nH2O. Our finding suggests that, as the cation size decreases from Cs to Na, stoichiometric A2A'2Ta3O9N compositions become more favorable than compounds with A-sites. This work provides a new perspective for the future design and synthesis of novel layered oxynitrides.

Structural and microstructural investigation of Sm and Sn doped BaTiO3

(Ba0.9Sm0.1) (Sn0.05Ti0.95) O3 (BSST) ceramic powders were synthesized by solid state reaction route and were pelletized and sintered at 1673 K for 4 h. The BSST thin film was also prepared by electron beam evaporation technique by using the sintered pellets. X-ray diffraction of the BSSTO confirmed that the material has formed in crystalline nature and also in single phase. Raman spectroscopy was used to study the morphology, structure and phase transition behaviour of BSST bulk as well as thin film. The Raman analysis indicated that the film formed at 973 K by electron beam evaporation is less crystalline than that of the bulk BSST due to inadequate substrate temperature.

Structural transition and photoluminescence behavior of (V2O5)1-x (Ag0.33V2O5)x (x = 0 to 0.1) nanocomposites

The two phase (V2O5)1-x(Ag0.33V2O5)x (x = 0, 0.05, 0.075 and 0.1) nanocomposites were synthesized through one step hydrothermal process. The X-ray diffraction followed by two phase Rietveld refinement confirms the crystallization of V2O5 and Ag0.33V2O5 phases in the Pmmn (orthorhombic) and C21 (monoclinic) symmetry respectively without any impurity phase. Furthermore, the FE-SEM, EDX, PL, UV–vis and XPS characterization were carried out for microstructural, optical and chemical studies. The formation of Ag0.33V2O5 nano-belts with average length and width of 3–4 μm and 40–50 nm respectively, were observed in the electron micrograph. Moreover, the XPS study confirms the constituent element are in expected oxidation states with Vanadium in only + 5 (V+5) for V2O5 and in mixed states (V+5 and V+4) for 10 % Ag0.33V2O5 nanocomposite. The photoluminescence spectra of these nanocomposite depicts two broad emission peaks located around 570 nm and 707 nm due to indirect inter-band and mid-state energy states transitions, respectively. PL also prove the increase in oxygen vacancies by loading of Ag in V2O5 matrix. The optical absorption of Ag0.33V2O5 represents a decrease in the energy band gap (2.10–1.97 eV) by adding Ag concentration in the V2O5, which also proved the semiconductor to metal transition (SMT).

Effect of Gd3+/Ti4+ heterovalent substitution on the crystal structure, morphology, optical properties, and phase transition behavior of bismuth layer-structured SrBi2Nb2O9

The double-layer Aurivillius compounds Sr1-xGdxBi2Nb2-xTixO9 (x ​= ​0, 0.2, 0.4, 0.6, 0.8, and 1), which have the potential to be developed as a ferroelectric material, have been synthesized using the molten salt method. This study aims to investigate the effect of the simultaneous substitution of Gd3+ and Ti4+ ions in SrBi2Nb2O9 on the phase formation, crystal structure, morphology, and ferroelectric properties. The single-phase product with A21am orthorhombic structure was obtained for all samples by X-ray diffraction analysis. The unit cell becomes more orthorhombic with increasing x as the degree of tetragonality increases. SEM micrographs demonstrate the plate-like grain morphology with an anisotropic growth direction, and the grain is smaller in size with increasing x. FTIR spectra indicate that cation substitution was successful, especially Ti4+ ions at the B-site. With increasing x, the ferroelectric transition temperature (Tc) increases, which has been explained in terms of a reduction in the tetragonality. The open hysteresis loops provide evidence of ferroelectric properties which is consistent with the trend of room-temperature dielectric constant. The optical bandgap value is proportional to the trend of the dielectric characteristics of the samples.

Direct determination of the π-helix structure and helix transition behavior of poly(β-phenethyl l-aspartate) via synchrotron X-ray diffraction.

The helix-sense inversions of poly(β-phenethyl l-aspartate) (2P) and diblock copolymers (2P-3P), with 2P and poly(β-phenylpropyl l-aspartate) (3P) blocks, were studied in their solid states using synchrotron wide-angle X-ray diffraction and small-angle X-ray scattering. The characteristic parameters of the π-helix structure of 2P were directly determined in situ after the helix transition at a high temperature. In the 2P-3P block copolymers, the main chains of the 3P blocks initially convert from right- to left-handed α-helices, and then the 2P blocks convert irreversibly from right-handed α-helices to left-handed π-helices. The chemical structures of the side chains of poly(l-aspartic acid ester)s significantly affect their helix transition behaviors.

Novel properties of stearic acid / MXene - Graphene oxide shape - Stabilized phase change material: Ascended phase transition temperature and hierarchical transition

To develop novel materials with active photothermal conversion and latent heat storage properties, the shape-stabilized phase change material was fabricated via self-assembly method employing stearic acid (SA) as heat storage medium, graphene oxide and MXene as hybrid matrix (GM) and photothermal conversion agent. The morphology, structure, properties and phase transition behavior were investigated by various techniques. The results shown that SA/GM has sandwich-like structure and SA is confined between matrix nanosheets in multiple crystallographic forms. Due to the superposition of host-guest interaction and intrinsic van der Waals force between nanosheets, the primary melting temperature of SA/GM climbs 27.7 °C approximately than that of SA, as well as the total latent heat decreases by 28.55%–30.85% compared with theoretical values. The confinement effect increases the crystallization activation energy of confined SA, and leads to the formation of non-phase transition layer, transitional confinement layer and proximate bulk layer. However, the above observations are applicable to fatty acids/GM, only the suppressed latent heat occurs in all GM-matrix composites. In addition, the SA/GM7 has excellent photothermal conversion efficiency, as high as 93.34%, and gradient latent heat storage capacity, 45.96 J g −1 at 74.43 °C and 91.19 J g −1 at 92.37 °C. Stearic acid/Mxene - graphene oxide (SA/GM) composite was fabricated though self-assembly method. The confined SA exists in multiple crystal forms and shows abnormal properties, including the ascended phase transition temperature, hierarchical phase transition and the formation of confined layer. The SA/GM presents excellent photothermal conversion efficiency and gradient heat storage/release performances. • SA/GM was self-assembled by the inherent forces of matrix nanosheets and host-guest interaction. • The main melting temperature of SA/GM increased by 27.7 °C approximately. • Non-phase change layer, transitional confinement layer and proximate bulk layer exist in SA/GM. • Ascended transition temperature and stratified phase transition are applicable to fatty acids/GM.

Characterization of single-crystal macro-fiber composite-based piezoelectric energy harvesters in various temperature and humidity environments

Single-crystal macro-fiber composite (SFC)-based piezoelectric energy harvesters (PEHs) have garnered significant interest for use in self-powered low-power-consumption devices. The outdoor deployment of PEHs subjects SFCs to a wide range of temperatures and humidities, which affects their electrical and mechanical properties and thus their output power efficiency. In this study, the energy-harvesting performance of undoped and 1 mol.% Mn-doped PMN-PZT SFC-based PEHs was investigated by varying the temperatures from −20 to 70 °C and the relative humidity (RH) from 10 to 90% under different base acceleration conditions. Both PEHs showed a gradual decrease in resonance frequency and optimum load resistance with increasing temperature, whereas the root mean square (RMS) power (Prms) was strongly composition-dependent. In particular, the Prms of the undoped SFC-based PEH displayed an inverse relationship with the climatic temperature, whereas the Mn-doped SFC-based PEH showed a peak Prms at 40 °C. In addition, the overall Prms loss concerning the optimal temperature for undoped and Mn-doped samples in the measured temperature range was 50% and 18%, respectively. These different characteristics according to the temperature environment could be owing to the different structural transition behaviors (i.e., Curie temperatures) of the piezoelectric single-crystal fibers. Short-term humidity exposure had a negligible effect on the energy-harvesting efficacy of the PEHs at room temperature (25 °C); however, the efficacy was slightly influenced under harsh conditions (50 °C and >60% RH). This study provides an environmental reliability evaluation of SFC-based PEHs for future practical use.

The Effect of the Substituent Positions on Self-Assembly Behaviors of Liquid-Crystalline 1,3,4,6,9b-Pentaazaphenalene Derivatives

Abstract We describe the syntheses and phase transition behaviors of liquid crystals composed of triangular π-conjugated molecules, 1,3,4,6,9b-pentaazaphenalene (5AP). Three types of 5AP derivatives having 3,4,5-tris(dodecyloxy)phenyl ((OC12)3Ph) were prepared by changing substituent positions. From thermal and structural analyses, liquid crystalline phases were observed from all derivatives. According to structural data and phase transition behaviors, it was suggested that the positions of the substituents significantly influence molecular alignments in liquid crystals as well as thermal properties. In particular, the columnar structures, which are favorable for expressing efficient carrier transportation, were observed in the 5AP derivative. These results suggest that the 5AP scaffold could be a platform for constructing a variety of aggregated structures by slightly different patterns of the molecular structures. Plausible models for these transitions are discussed.

Microstructure and transition behavior of Fe&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;P-based first-order magnetic phase-transition alloys

<p indent="0mm">Fe₂P-based first-order magnetic phase-transition alloys have been considered as one of the best candidates for room-temperature magnetic refrigeration applications due to their low cost, tunable working temperature range and superior magnetocaloric performance. Previous studies mainly focused on optimizing the magnetocaloric properties as well as uncovering the spin-lattice-electronic multi-coupling in the Fe₂P-based alloys, while the structure and phase transition behavior at the micrometer scale have rarely been reported. In the present study, we performed intensive studies on the microstructure and phase transition behavior in the Fe₂P-based alloys by means of transmission electron microscopy and X-ray powder diffraction (XRD). SiO₂ and Fe₃Si-type secondary phases with micrometer or sub-micrometer sizes are distributed along the grain boundary. <italic>In-situ</italic> XRD measurements indicate that the paramagnetic-ferromagnetic (PM-FM) transition is accompanied with significant lattice distortion in the hexagonal structure. The hexagonal unit cell is expanded by approximately 0.8% along the <italic>a</italic> axis, while it is contracted by about 1.8% along the <italic>c</italic> axis. The serve lattice distortion will induce large elastic energy, raise the energy barrier and thus bring about thermal hysteresis for the first-order magnetic transition. The magnetic transition-induced lattice distortion is more easily accommodated in the regions close to secondary phases and grain boundaries, where the atomic arrangement is more disordered. As a result, the nucleation of the PM-FM transition is found to start from the defect areas. However, the secondary phases and grain boundaries pin the domain walls, which hinders the growth of the ferromagnetic phase. The pinning effect of the defects will increase the energy barrier, causing an increase in the thermal hysteresis and the critical driven field for the first-order PM-FM transition. As a consequence, in order to further optimize the magnetocaloric performance, more efforts should made on tailoring both the intrinsic (e.g., lattice discontinuity) and extrinsic (e.g., size and distribution of the secondary phases) factors dominating the first-order magnetic transition of Fe₂P-based alloys.

Theoretical investigations on HgTe chalcogenide materials under high pressure

First principle computations based on Density Functional Theory are made to investigate structural, mechanical, electronic properties and phase transition behaviors of HgTe chalcogenide material. It is obtained that the phase transition sequence of HgTe material is Zincblende → Cinnabar → Rocksalt → Cmcm → CsCl at 2.35 GPa, 5.95 GPa, 14.29 GPa, 52.37 GPa, respectively. The negative and values of the CsCl structure under ambient conditions indicate that this structure is mechanically unstable against the applied deformations. The small values of the elastic constants of HgTe in the cinnabar structure reveal that this structure is less resistant to deformations. The low value of tetragonal shear constant Cs of the parent phase reflects the elastic instability leading to a pressure-induced phase transition. According to our isotropic mechanical results obtained from the Voigt-Reuss-Hill (VRH) approach, the ductility behavior improves in the rocksalt and Cmcm structures which are high-pressure phases. The zincblende and cinnabar structures show semimetal and semiconductor properties in the electronic band calculations, respectively, while rocksalt, Cmcm and CsCl structures are found to be of metallic character.

Experimental observations and density functional simulations on the structural transition behavior of a two-dimensional transition-metal dichalcogenide

In this work, we show an obvious evidence of nondestructive Raman spectra for the structural transition, i.e., the existence of a charge density wave (CDW) in monolayer 2H-TaS2, which can exhibit a much higher transition temperature than bulk and results in additional vibrational modes, indicating strong interactions with light. Furthermore, we reveal that the degenerate breath and wiggle modes of 2H-TaS2 originated from the periodic lattice distortion can be probed using the optical methods. Since recently several light-tunable devices have been proposed based on the CDW phase transition of 1 T-TaS2, our study and in particular, the theoretical results will be very helpful for understanding and designing electronic devices based on the CDW of 2H-TaS2.

Fluoride ion field emission from a ZBLAC glass emitter

F− ion conducting 60ZrF4·30BaF2·LaF3·2AlF3·7CsF (mol%) with outer mol% of xIn2O3 (x = 0, 5, 10) glasses were prepared using a conventional melting method, and structure and glass transition behavior were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Raman spectroscopy. Impedance measurement reveals the glass with x = 10 shows F− ion conductivity of 5 × 10−6 S/cm at 200 °C. F− ion emission measurement was carried out for the first time using a sharpened glass tip, and the emission current was observed above the acceleration voltage of 2.5 kV at 200 °C and 1 × 10−4 Pa. After the F− emission measurement, fluorine was detected on a Cu target substrate by using an energy-dispersive X-ray spectrometer. However, a small amount of glass component was also detected on the target substrate, suggesting the glass tip may also decompose. A good linear correlation is obtained between log(current) and the square root of the voltage, suggesting the emission current of F− ion from the tip of glass is expressed by Schottky model.