Jun Kuwano

Order-disorder of the A-site ions and lithium ion conductivity in the perovskite solid solution La0.67-xLi3xTiO3 (x = 0.11)

Abstract The A-site-deficient perovskite solid solution (ADPESS) La0.67−xLi3xTiO3 (x=0.11) underwent an order–disorder transition reversibly with a reversible change in ionic conductivity. The cubic, disordered form (a=ap) was obtained by quenching from temperatures above ∼1150°C, while the tetragonal, ordered form (a=ap, c≈2ap), by annealing at temperatures below ∼1150°C. Since controlled thermodynamically, the extent of ordering of La ions could be changed reversibly by annealing in a range of 600–1150°C. The equilibrated order parameter S increased continuously from 0 at 1150°C to ∼0.83 at 600°C with decreasing annealing temperature. The bulk ionic conductivity at 25°C had a small maximum at S≈0.2 and decreased increasingly rapidly with increasing extent of ordering in a range of S>0.2. The tetragonal distortion of the subcell began at S≈0.2. The distortion became more manifest and the lattice parameters a contracted more with increasing extent of ordering in a range of S>0.2. The decrease in ionic conductivity is attributed to an increase in activation energy for ionic conduction, which is presumably associated with the contraction of the lattice parameter a of the subcell.

Electrochemical polymerization of thiophene under ultrasonic field

Abstract Films of polythiophene were prepared by electrochemical oxidation under ultrasonic field. The ultrasonic irradiation had an influence on the conditions and the properties of the as-polymerized films. In the absence of ultrasonic irradiation, the as-polymerized films became brittle gradually when the electrolytic current density exceeded the value of 5 mA/cm 2 . Whereas flexible and tough films with the tensile modulus of 3.2 GPa and strength of 90 MPa were obtained even at a high current density of 10 mA/cm 2 with ultrasonic irradiation. The doping level increased with increasing electrolytic current density, further, at a given current density, the levels for the irradiated series were higher than those for unirradiated series, which lead to a high electrical conductivity (130–150 S/cm) for the irradiated series. Cyclic voltammetry implied a higher diffusion rate for the films prepared under ultrasonic field compared with that for prepared without irradiation.

Lithium ion conductivity of A-site deficient perovskite solid solutions

Abstract Over twenty of A-site deficient perovskite solid solution with Li + ion conductivity (Li-ADPESSs) were prepared with the M and Li concentration fixed at M 0.56 Li 0.33 TiO 3 in the five series: (A) (La 1− X Nd X ) 0.56 Li 0.33 TiO 3 , (B) La 0.56 Li 0.33 M(IV) X Ti 1− X O 3 [M(IV)=Zr,Hf], (C) (Ca 1− X Sr X ) 0.56 Li 0.33 Ta 0.56 Ti 0.44 O 3 , (D) (Ca 1− X Sr X ) 0.56 Li 0.33 Fe 0.225 Ta 0.775 O 3 , E) Sr 0.56 Li 0.33 M(|||) 0.225 Ta 0.775 O 3 [M(|||)=Cr,Fe,Co,Ga,Y]. Except for the few, the quenched samples were the α-form with disordered arrangement of the A-site ions. The relation between bulk conductivity ( σ b ) and the cube root ( V 1/3 ) of the perovskite cell volume showed a maximum at V 1/3 ≈387 pm for the series A, B and at V 1/3 ≈395 pm for the series C–E, respectively. The perovskite framework containing less covalent, large cations calls for a larger optimal cell volume for fast conduction.

Formation of perovskite solid solutions and lithium-ion conductivity in the compositions, Li2xSr1-2xMIII0.5-xTa0.5+xO3 (M = Cr, Fe, Co, Al, Ga, In, Y)

Formation of solid solutions with perovskite structure and ionic conductivity have been investigated in the systems Li 2x Sr 1-2x M III 0.5-x Ta 0.5+x O 3 ( M = Cr, Fe, Co, Al, Ga, In, Y). Perovskite solid solutions formed in ranges of x ≤ 0.25 for M = Fe, Cr, x < 0.22 for Ga and x < ∼ 0.16 for M = Co, In. No single-phase samples of perovskite solid solution were prepared for M = Al, Y. The solid solutions Li 0.5 Sr 0.5 M III 0.25 Ta 0.75 O 3 (M = Fe, Cr; x = 0.25) had high bulk conductivities of 1.0 X 10 -4 S cm -1 and 6.0 x 10 -5 S cm -1 at room temperature, respectively. The former value was the highest of those reported to date for lithium electrolytes based on tantalates. They were simple cubic perovskites (space group: Pm3m; a = 396.39 pm for Fe, a = 395.03 pm for Cr), indicating that the Li and Sr ions, and the M (Fe or Cr) and Ta ions are randomly distributed over the A-sites and B-sites, respectively. Frame emission analysis for Li in both sintered pellets revealed that the loss of the Li content took place during sintering. The high conductivity is probably attributed to an A-site deficient perovskite phase resulting from the loss. The perovskite solid solutions in the other systems exhibited conductivities as low as 10 -7 -10 -8 S cm -1 . The Fe-and Cr-containing solid solutions are the first of tantalate-based perovskites with high Li-ion conductivity.

Ionic conductivity of poly(ethylene glycol)−LiCF3SO3-ultrafine SiO2 composite electrolytes : effects of addition of the surfactant lithium dodecylsulfate

Abstract The addition of a proper amount of the surfactant lithium dodecylsulfate enhances the ionic conductivity of the composites consisting of low molecular weight poly(ethylene glycol), LiCF 3 SO 3 and ultrafine SiO 2 by a factor of five or ten. The optimized conductivity is 4.8 × 10 −5 Scm −1 at 40 °C. The enhancement is associated with the oriented adsorption of the surfactant on the surface of the SiO 2 particles.

Ionic conductivity of LiM2(PO4)3 (M=Ti, Zr, Hf) and related compositions

Abstract This paper describes ionic conductivity and phase transition in the Li-substituted NASICONs LiM 2 (PO 4 ) 3 (M=Ti, Zr, Hf) and in the systems LiM 2 (PO 4 ) 3 Li 2 O, LiZr 2 (PO 4 ) 3 Li 3 PO 4 and LiZr 2− x M x (PO 4 ) 3 . The results demonstrate that the conductivity enhancement in various LiM 2 (PO 4 ) 3 -lithium salt systems is associated with the formation of solid solutions based on the substitution M 4+ ⇆4Li + .

Optimum design for the sensing electrode mixtures of PbSnF4-based oxygen sensors for fast response at ambient temperature

Abstract The amperometric oxygen sensors of the type, Ag|Ag 6 I 4 WO 4 |PbSnF 4 |sensing electrode (a mixture of iron(II) phthalocyanine (FePc), PbSnF 4 and a whisker material) have been fabricated and effects of the incorporated whiskers on response properties have been examined to design the optimum sensing electrode mixture. The selected whiskers were several 9Al 2 O 3 ·2B 2 O 3 and TiO 2 whiskers different in length and conductivity (with or without conductive SnO 2 coating film). Fast response comparable to that of galvanic-cell-type sensors was realized with the sensing electrode mixture designed on the basis of the following two points: (1) the sensing electrode should be a ternary mixture of whiskers, FePc and PbSnF 4 with a volume ratio of 1:7:2; (2) the whiskers should have a length around 20 μm, an aspect ratio of about 20 and a good electronic conductivity. The mean response time, 25 s, was to date the shortest of those of known solid-state electrochemical sensors at room temperature. The incorporation also greatly improved other response properties such as transient behavior, drifts and hysteresis. The roles of the incorporated conductive whiskers are to form the conductive whisker networks in the sensing electrode mixture and to make the reduction sites of oxygen molecules electrochemically uniform by localizing the sites along the networks.

Fast amperometric response of ambient temperature oxygen sensor based on PbSnF4; iron (II) phthalcyanine-based sensing electrodes containing carbon microbeads

Abstract Several kinds of carbon microbeads and noble metal powders have been tested as an additive to the iron (II) phthalocyanine-based sensing electrode (SE) for the amperometric oxygen sensors; Ag|Ag 6 I 4 WO 4 |PbSnF 4 |SE, O 2 . The use of the SE containing surface-modified carbon microbeads enables the sensors not only to respond fast at room temperature but to exhibit the highest sensitivity. Furthermore, it is capable of determining oxygen partial pressures of 2–750 kPa in a wide operating pressure range 10 kPa–3.5MPa.

Silver ion conducting glasses and some applications

The glass-forming region, ionic conductivity and glass transition temperatures are determined in the system AgI-Ag 2 O-WO 3 . The glasses have silver ion conductivities of 10 −2 to 10 −3 S cm −1 at 25 o C and are characterized by high glass transition temperature, over 130 o C. Two new chemical sensors and a recording technique by electron beam irradiation are proposed as applications of silver ion conducting glasses

New lithium-ion conducting compounds 3Li3N-MI (M = Li, Na, K, Rb) and their application to solid-state lithium-ion cells

Abstract In the quasi-binary systems Li 3 N-MI (M = Li, Na, K, Rb) new intermediate compounds 3Li 3 N-MI were synthesized by a solid-state reaction between Li 3 N and MI at 600°C. They were isomorphous and had a tetragonal unit cell. Their sintered bodies exhibited lithium-ion conductivity of 1.1 × 10 −4 –7.0 × 10 −5 S cm −1 at room temperature. The grain boundary resistances were negligibly small because of their good sinterability. The decomposition voltages were approximately 2.5–2.8 V, much higher than that of Li 3 N. Even the compacts of the powdered compounds showed total conductivities more than 10 −5 S cm −1 . This allowed the cell construction of the solid-state lithium-ion cell, C/3Li 3 N-KI/LiTiS 2 , simply by pressing the powdered electrolyte and electrode materials. The cell was able to charge and to discharge at a constant current of 15 μA cm −2 at room temperature; however, severe polarization in the positive electrodes limited the charge/discharge performance.