Ionic conductivity of polymer electrolyte membranes based on polyphosphazene with oligo(propylene oxide) side chains

A polyphosphazene [NP(NHR)₂]_n with oligo[propylene oxide] side chains − R = –[CH(CH₃)–CH₂O]_m–CH₃ (m = 6 – 10) was synthesized by living cationic polymerisation and polymer-analogue substitution of chlorine from the intermediate precursor [NPCl₂]_n using the corresponding primary amine RNH₂. The polymer had an average molecular weight of 3.3 × 10⁵ D. Polymer electrolytes with different concentrations of dissolved lithium triflate (LiCF₃SO₃) were prepared. Mechanically stable polymer electrolyte membranes were formed using UV radiation induced crosslinking of the polymer salt mixture in the presence of benzophenone as photoinitiator. The glass transition temperature of the parent polymer was found to be − 75 °C before cross linking. It increases after crosslinking and with increasing amounts of salt to a maximum of − 55 °C for 20 wt.% LiCF₃SO₃. The ionic conductivity was determined by impedance spectroscopy in the temperature range 0–80 °C. The highest conductivity was found for a salt concentration of 20 wt.% LiCF₃SO₃: 6.5 × 10^− 6 S·cm^− 1 at 20 °C and 2.8 × 10^− 4 S cm^− 1 at 80 °C. The temperature dependence of the conductivities was well described by the MIGRATION concept.     

Growth and properties of Li,Ta modified (K,Na)NbO3 lead‐free piezoelectric single crystals

Li, Ta modified (K,Na)NbO₃ single crystals with the size of 18 mm × 18 mm × 10 mm were successfully grown by top‐seeded solution growth method, with orthorhombic–tetra‐gonal phase transition temperature ～79 °C and Curie temperature ～276 °C. The electromechanical coupling factors k₃₃ and k_t were found to be ～88% and ～65%, respectively. The piezoelectric coefficient d₃₃ for the [001]_c poled crystals reached 255 pC/N. In addition, the electromechanical coupling factor exhibited high stability over the temperature range of –50 °C to 70 °C, making these lead free crystals good candidates for electromechanical applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal expansion measurements for estimating vacancy concentration in X-ray irradiated KCl single crystals

A sensitive capacitance technique is used for measuring changes in length (Δl) of KCl single crystals with temperature in the region 30–300°C. These measurements have been taken on KCl in (i) as-cleaved (ii) X-ray irradiated (iii) quenched and X-ray irradiated conditions (X-ray irradiation was always done at room temperature (≈ 30°C). The linear coefficient of thermal expansion (α) of the as-cleaved sample is 40.8 × 10^-6°C^-1. Variation of Δl with temperature in X-ray irradiated crystal shows two regions: (a) 30–180°C where α is 48.1 × 10^-6°C^-1, (b) 180–300°C where α is 40.4 × 10^-6°C^-1. Similar behaviour is exhibited by quenched and later X-ray irradiated KCl the first region is up to 140°C, beyond which the second region takes over. From these data, concentration of vacancies in X-ray irradiated KCl at room temperature is calculated to be 3.4 × 10¹⁷ cm^-3 which is in fairly good agreement with the value obtained from F-band absorption measurements on the sample. An attempt has been made to understand these results.     

Leed,aes and photoemission measurements of epitaxially grown GaAs(001), (111)A and (1̄1̄1̄)B surfaces and their behaviour upon cs adsorption

Epitaxially grown GaAs(001), (111) and (1?1?1?) surfaces and their behaviour on Cs adsorption are studied by LEED, AES and photoemission. Upon heat treatment the clean GaAs(001) surface shows all the structures of the As-stabilized to the Ga-stabilized surface. By careful annealing it is also possible to obtain the As-stabilized surface from the Ga-stabilized surface, which must be due to the diffusion of As from the bulk to the surface. The As-stabilized surface can be recovered from the Ga-stabilized surface by treating the surface at 400°C in an AsH₃ atmosphere. The Cs coverage of all these surfaces is linear with the dosage and shows a sharp breakpoint at 5.3 × 10¹⁴ atoms cm^?2. The photoemission reaches a maximum precisely at the dosage of this break point for the GaAs(001) and GaAs(1?1?1?) surface, whereas for the GaAs(111) surface the maximum in the photoemission is reached at a higher dosage of 6.5 × 10¹⁴ atoms cm^?2. The maximum photoemission from all surfaces is in the order of 50μA Im^?1 for white light (T = 2850 K). LEED measurements show that Cs adsorbs as an amorphous layer on these surfaces at room temperature. Heat treatment of the Cs-activated GaAs (001) surface shows a stability region of 4.7 × 10¹⁴ atoms cm^?2 at 260dgC and one of 2.7 × 10¹⁴ atoms cm^?2 at 340°C without any ordering of the Cs atoms. Heat treatment of the Cs-activated GaAs(111) crystal shows a gradual desorption of Cs up to a coverage of 1 × 10¹⁴ atoms cm^?2, which is stable at 360°C and where LEED shows the formation of the GaAs(111) (√7 × √7)Cs structure. Heat treatment of the Cs-activated GaAs(1?1?1?) crystal shows a stability region at 260°C with a coverage of 3.8 × 10¹⁴ atoms cm^?2 with ordering of the Cs atoms in a GaAs(1?1?1?) (4 × 4)Cs structure and at 340°C a further stability region with a coverage of 1 × 10¹⁴ at cm^?2 with the formation of a GaAs(1?1?1?) (√21 × √21)Cs structure. Possible models of the GaAs(1?1?1?) (4 × 4)Cs, GaAs(1?1?1?)(√21 × √21)Cs and GaAs(111) (√7 × √7)Cs structures are given.     

Electrocaloric effect in antiferroelectric PbZrO3 thin films

Antiferroelectric PbZrO₃ thin films have been deposited on Pt(111)/Ti/SiO₂/Si substrate by polymer modified sol–gel route. Temperature dependent P –E hysteresis loops have been measured at 51 MV/m within a temperature range of 40 °C to 330 °C. The maximum electrocaloric effect ～0.224 × 10^–6 K mV^–1 has been observed near the dielectric phase transition temperature (235 °C) of the thin films. The electrocaloric effect and its strong temperature dependence have been attributed to nearly first‐order phase transition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ionic transport in the lithium nitride bromides,Li6NBr3 and Li1 3N4Br

The ionic and electronic conductivities of the lithium nitride bromides Li₆NBr₃ and Li_{1 3}N₄Br have been studied in the temperature range from 50 to 220°C and 120 to 450°C, respectively. Both compounds are practically pure lithium ion conductors with negligible electronic contribution. Li₆NBr₃ has an ionic conductivity Ω of 2 × 10^-6Ω^-1cm^-1 at 100°C and an activation enthalpy for σT of 0.46 eV. Li_{1 3}N₄Br shows a phase transition at about 230°C. The activation enthalpy for σT is 0.73 eV below and 0.47 eV above this temperature. The conductivities at 150 and 300°C were found to be 3.5 × 10^-6 Ω^-1cm^-1 and 1.4 × 10^-3Ω^-1cm^-1, respectively. The crystal structure is hexagonal at room temperature with $\text{a = 7.415 (1)}\text{A}\text{?}$ and $\text{c = 3.865 (1)}\text{A}\text{?}$.     

Shear‐Enhanced Nucleation of Isotactic Polypropylene in Limited Space

The nucleation rate was measured by directly counting the number of nuclei, which were developed while an isotactic polypropylene melt was flowing under shear in a thin film. The nucleation rate was enhanced with an increased rate of shear, e.g., by a factor of 10 larger at the rate of shear of 14 s^?1 compared with the quiescent state, at 134°C. The ratio of the shear‐enhanced nucleation rate to the nucleation rate in the quiescent state was larger at a higher temperature of crystallization, i.e., about 10 times at 134°C to 590 times at 140°C. The increase of the nucleation rate under shear flow was explained by a reduction of the lateral and end (fold) surface free energies; the product σ _s ² σ _e decreased to 3.2×10^?7 for the sheared melt, from 6.0×10^?7 (J m^?2)³ for the isotropic state. The free energy reduction was caused by transition of the nucleus formation mode from three‐dimensional folded chain nuclei to two‐dimensional bundle nuclei, in which chains lie down on the glass substrate, aligning parallel to the flow direction.     

The GaP(001) surface and the adsorption of Cs

GaP(001) cleaned by argon-ion bombardment and annealed at 500°C showed the Ga-stabilized GaP(001)(4 × 2) structure. Only treatment in 10^?5 Torr PH₃ at 500°C gave the P-stabilized GaP(001)(1 × 2) structure. The AES peak ratio $\text{P}\text{Ga}$ is 2 for the (4 × 2) and 3.5 for the (1 × 2) structure. Cs adsorbs with a sticking probability of unity up to 5 × 10¹⁴ Cs atoms cm^?2 and a lower one at higher coverages. The photoemission measured with uv light of 3660 Å showed a maximum at the coverage of 5 × 10¹⁴ atoms cm^?2. Cs adsorbs amorphously at room temperature, but heat treatment gives ordered structures, which are thought to be reconstructed GaP(001) structures induced by Cs. The LEED patterns showed the GaP(001)(1 × 2) Cs structure formed at 180°C for 10 h with a Cs coverage of 5 × 10¹⁴ atoms cm^?2, the GaP(001)(1 × 4) Cs formed at 210°C for 10 hours with a Cs coverage of 2.7 × 10¹⁴ atoms cm^?2, the GaP(001)(7 × 1) and the high temperature GaP(001)(1 × 4), the latter two with very low Cs content. Desorption measurements show three stability regions: (a) between 25–150°C for coverages greater than 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.2 eV; (b) between 180–200°C with a coverage of 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.8 eV; (c) between 210–400°C with a coverage of 2.7 × 10¹⁴ atoms cm^?2, and an activation energy of 2.5 eV.     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

Diffuse LEED intensities of disordered crystal surfaces: III. LEED investigation of the disordered (110) surface of gold

The LEED pattern of clean (101) surfaces of Au show a characteristic (1 × 2) superstructure. The diffuseness of reflections in the reciprocal [010] direction is caused by one-dimensional disorder of chains, strictly ordered into spatial [101̄] direction. There is a transition from this disordered superstructure to the normal (1 × 1) structure at 420 + 15°C. The angular profiles of the $\text{(0}\text{1}\text{2}\text{)}$ and (01) beam are measured at various temperatures and with constant energy and angles of incidence of the primary beam. The beam profiles are deconvoluted approximately with the instrument response function.     

Minimum metallic conductivity in a thin crystal

Electrical conductivities of thin crystals of Bi₂(Te,S)₃ measured from 4.2°K to 300°K fall into four regions: 1) σ < 1.3×10^?5 S with positive temperature coefficient of conductivity; 2) 1.3×10^?5 S < σ < 1.4×10^?5 S with temperature independent conductivity; 3) 1.4×10^?5 S σ < 4×10^?5 S with negative temperature coefficient of conductivity, and 4) σ > 4×10^?5 S with hardly any temperature dependence. A disproportionately high fraction of samples falls into the second range; 1.3×10^?5 S < σ < 1.4×10^?5 S.     

Annealing characteristics of highly doped ion implanted phosphorus layers in silicon

A combination of sheet resistance, stripping and Hall effect measurements have been made on phosphorus layers implanted into silicon at 40 and 100 keV with doses between 1 × 10¹⁵ and 5 × 10¹⁶ atoms/cm². The implants were made at room temperature and 450°C. After annealing at 650°C, the profile of electrically active phosphorus following a high dose room temperature implant, was found to be flat topped with a concentration of approximately 5 × 10²⁰/cm³. Very little diffusion occurred when annealing to 850°C where the free electron concentration increased to approximately 1.5 × 10²¹/cm³. Highly doped channeled tails were found when implanting at 450°C along the 〈110〉 direction and damage was being continuously annealed out preventing the formation of an amorphous phase. The rapid diffusion of the profile into the bulk found when annealing between 650°C and 850°C was speculated to be due to the presence of a dense dislocation entanglement in these layers following a hot implant.     

Nanoscopic measurements of the electrostriction responses in P(VDF/TrFE) ultra-thin-film copolymer using atomic force microscopy

Atomic force microscopy (AFM) has been used as a new method to perform nanoscale measurements of the electrostriction coefficients in the lamellae structure of the ferroelectric P(VDF/TrFE) 73/27 copolymers. The result found shows that the electrostriction coefficient inside (in the middle of) the lamella crystals is 6×10^-19 (m²V^-2), which is three times larger than that at the boundary, 2×10^-19 (m²V^-2). To explain the dependence of the electrostriction coefficients with those two regions, some suggestions are proposed. By heat treatment at 140 °C during 2 h, the sample changed its morphology as well as its crystallinity; the amorphous phase is much reduced and the degree of the crystallinity inside the lamellae is higher than that in the border. Also, it is suggested that in the lamellae’s boundary the macromolecular chains come to an end, or one monolayer folds over the other layer. In this case, the electrostriction was suppressed due to the loss of surface energy in the lamellae’s boundary. The achievements will supply a guideline to develop new and better devices for electromechanical and actuator applications. Received: 23 June 2000 / Accepted: 23 August 2000 / Published online: 5 October 2000     

Polyethylene Structure as a Function of Temperature: An EDXD Investigation

Polyethylene structure has been investigated by energy dispersive X‐ray diffraction (EDXD) as a function of temperature below the melting point, via Rietveld refinement. The behavior was studied at four temperatures, namely 25, 40, 70, and 88°C. In this range the structure undergoes a regular volume expansion that may be expressed in terms of specific volume ratio as V_E/V_25°C=0.991(2)+4.0(5)×10^?4×T(°C). The variation is almost completely taken up by the a cell parameter and results, apart for minor intrachain arrangements, in an increased distance between polymer chains.     

Polymer electrolytes based on polycarbonates and their electrochemical and thermal properties

Polycarbonates (4a–d) with various side chain lengths were synthesized by the reaction of 1,4-bis(hydroxyethoxy)benzene derivatives and triphosgene in the presence of pyridine. The polymer electrolytes composed of 4a–d with lithium bis(trifluoromethanesulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) were prepared, and their ionic conductivities and thermal and electrochemical properties were investigated. 4d-Based polymer electrolyte showed the highest ionic conductivity values of 1.0?×?10^?4?S/cm at 80 °C and 1.5?×?10^?6?S/cm at 30 °C, respectively, at the [LiTFSI]/[repeating unit] ratio of 1/2. Ionic conductivities of these polycarbonate-based polymer electrolytes showed the tendency of increase with increasing the chain length of oxyethylene moieties as side chains, suggestive of increased steric hindrance by side chains. Unique properties were observed for the 4a(n?=?0)-based polymer electrolyte without an oxyethylene moiety. All of polycarbonate-based polymer electrolytes showed good electrochemical and thermal stabilities as polymer electrolytes for battery application.     

Solid-precursor vaporizer for aerosol reactors: Synthesis of magnesium aluminate nanoparticles by thermal decomposition of magnesium aluminum tert-butoxide

A solid-precursor vaporizer for laboratory-scale aerosol reactors has been developed and successfully tested on the synthesis of magnesium aluminate (MgAl₂O₄) nanoparticles by thermal decomposition of magnesium aluminum tert-butoxide (Mg[Al(O^tBu)₄]₂), a single-source precursor, in a furnace aerosol reactor. The reactor temperature was varied from 600 to 1000°C with the precursor concentration at 6.4 × 10⁻⁶ mol/l. The atomic ratio of Al to Mg of produced particles was determined by XPS to be 2:1 and the primary particle size ranged from 28 to 55 nm. As-produced particles were all amorphous, but the particles further heated to 1000°C exhibited crystalline MgAl₂O₄ structures.     

Bromide ion conductivities of eutectic mixtures of quaternary ammonium bromides possessing long alkyl chains

Several quaternary ammonium bromides possessing long alkyl chains and their mixtures were found to be bromide ion conductors. The ionic conductivities of quaternary ammonium bromides themselves were lower than 10^?9 S cm^?1 at a room temperature. On the other hand, the eutectic mixtures of the quaternary ammonium bromides showed large increase of ionic conductivity. The best bromide ion conductors were found for the eutectic of Q₅, Q₇, Q₈, and Q₁₂: 4×10^?8 S cm^?1 at 30°C, and 6.3×10^?6 S cm^?1 at 50°C. Addition of asymmetric quarternary ammonium bromides had a negative effect on the ionic conductivity. These results were explained by a space filling factor in the solid.     

Dipole co-operative motions in an A-type carbonated apatite,Sr10(AsO4)6CO3

Relaxation of reorientable electric dipoles in A -type carbonated strontium arsenate, an apatite, has been studied with the thermally stimulated currents method. The fractional polarization technique permitted registration, in the range 9–428 K, of a separate current vs temperature curve for each small range of dipole-reorientation activation energies. Interpretation of these on a simple Debye model revealed four compensation temperatures, −100, 175, 392 and 573°C, with associated relaxation times τ_c = 2 × 10⁻⁶, 9 × 10⁻⁷, 2 × 10⁻⁶, and 1 × 10⁻⁵s, respectively. It is proposed that (1) the reorientable dipoles are primarily carbonate ions, and that (2) the co-operative phenomena associated with the 175°C and 392dgC temperatures are, respectively, a quasi-statically stabilized monoclinic-to-hexagonal phase transition and the onset of dynamical stabilization of the hexagonal phase.     

Thermal and electrochemical properties of poly(butylene sulfite)-based polymer electrolyte

Poly(butylene sulfite) (poly-1) was synthesized by cationic ring-opening polymerization of butylene sulfite (1), which was prepared by the reaction of 1,4-butanediol and thionyl chloride, with trifluoromethanesulfonic acid (TfOH) in bulk. The polymer electrolytes composed of poly-1 with lithium salts such as bis(trifluoromethanesulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and bis(fluorosulfonyl)imide (LiN(SO₂F)₂, LiFSI) were prepared, and their ionic conductivities, thermal, and electrochemical properties were investigated. Ionic conductivities of the polymer electrolytes for the poly-1/LiTFSI system increased with lithium salt concentrations, reached maximum values at the [LiTFSI]/[repeating unit] ratio of 1/10, and then decreased in further more salt concentrations. The highest ionic conductivity values at the [LiTFSI]/[repeating unit] ratio of 1/10 were 2.36?×?10^?4 S/cm at 80 °C and 1.01?×?10^?5 S/cm at 20 °C. On the other hand, ionic conductivities of the polymer electrolytes for the poly-1/LiFSI system increased with an increase in lithium salt concentrations, and ionic conductivity values at the [LiFSI]/[repeating unit] ratio of 1/1 were 1.25?×?10^?3 S/cm at 80 °C and 5.93?×?10^?5 S/cm at 20 °C. Glass transition temperature (T _g) increased with lithium salt concentrations for the poly-1/LiTFSI system, but T _g for the poly-1/LiFSI system was almost constant regardless of lithium salt concentrations. Both polymer electrolytes showed high transference number of lithium ion: 0.57 for the poly-1/LiTFSI system and 0.56 for the poly-1/LiFSI system, respectively. The polymer electrolytes for the poly-1/LiTFSI system were thermally more stable than those for the poly-1/LiFSI system.     

A new hyperbranched star polyether electrolyte with high ionic conductivity

Hyperbranched poly(glycidol) containing hydroxyl groups was firstly synthesized via anionic polymerization and then reacted with 2-bromoisobutyl bromide to form macroinitiator HPG-Br. Finally, a hyperbranched star polymer (HPG-PPEGMA) was successfully prepared by atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether methacrylate using HPG-Br as macroinitiator. The structures and properties of the obtained polymers were characterized by ¹H NMR, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The ionic conductivity of the polymer electrolytes composed of HPG-PPEGMA and lithium bis(trifluoromethanesulfonimide) (LiTFSI) was investigated via electrochemical impedance spectroscopy. The results showed that the room temperature ionic conductivity of the prepared hyperbranched star polymer electrolytes had a higher ionic conductivity. When [EO]/[Li] was 20, the ionic conductivity of the hyperbranched star polymer electrolyte was up to 1?×?10^?4 Scm^?1 at 30 °C. The onset decomposition temperature of the hyperbranched star polyether could reach 374 °C, indicating that the hyperbranched star polymer had a good thermal stability. The XRD results showed that the structure of the hyperbranched star polymer was beneficial to improve the ionic conductivity due to possessing a low degree of crystallinity.