Toshihiko Shigematsu

All-Solid-State Lithium Battery with LiCo0.3Ni0.7 O 2 Fine Powder as Cathode Materials with an Amorphous Sulfide Electrolyte

An all-solid-state battery was fabricated with LiCo 0.3 Ni 0.7 O 2 fine powder as cathode materials. The LiCo 0.3 Ni 0.7 O 2 fine powder was synthesized with oxalate decomposition methods and the average particle size of the powder was 2 μm diam. In the all-solid-state battery, a-60Li 2 S.40SiS 2 powder, which was prepared by a mechanical milling process, was used as the solid electrolyte. The anode was metallic indium foil 0.127 mm thick. The charge-discharge cycling test of the battery was carried out under a constant current density of 64 μA cm -2 with a 3.8 and 2.0 V charge-discharge criteria. The battery showed a rechargeable specific capacity of 98 mAh g -1 based on the cathode materials. The charge-discharge cycle efficiency of the battery was almost unity after the second cycle.

Magnetic Properties of Cementite (Fe1-xMex)3C, (Me; Cr or Ni)

Magnetization and Mossbauer absorption spectra have been measured on cementite substituted partially with Cr or Ni. The magnetic moment increases slightly with the increase of nickel concentration, while it decreases very abruptly from 1.9 µ B in Fe 3 C to 0.4 µ B in (Fe 0.799 Cr 0.201 ) 3 C. The internal field and the Curie temperature also decrease abruptly for the Cr-substituted cementite. The observed experimental results strongly indicate that the magnetic properties of the (Fe 1- x Me x ) 3 C system are closely analogous to those of γ Fe-Ni Invar alloy.

Mossbauer Studies of Very Thin Oxide Layer on Fe Surface

Very thin oxide layers on Fe metal surfaces with the thickness of ca. 10 A, are investigated by means of Mossbauer absorption spectroscopy using surface-selectively enriched samples. The oxide is similar to γ-Fe2O3 but has non-collinear spin arrangement at 4.2 K and is superparamagnetic at 300 K. The reduction of the recoilless fraction at 300 K is not drastic. Oxidation of Fe surfaces coated by Sb layers is also studied.

Invar Properties of Cementite (Fe1-xMex)3C, Me=Cr, Mn, Ni

Lattice parameters and thermal expansion have been measured on cementite partially substituted with Cr, Mn or Ni. The lattice-parameter-composition curves of (Fe 1- x Cr x ) 3 C and (Fe 1- x Mn x ) 3 C show notable anomalies at around x =0.08 for Cr and x =0.13 for Mn, where the Curie temperature of the alloys passed through the room temperature region. The lattice parameters at ferromagnetic state are larger than those at paramagnetic state. These compounds show an Invar type thermal expansion below the Curie temperature. These low thermal expansions in a narrow range around Fe 3 C are caused by the large positive spontaneous volume magnetostriction in the ferromagnetic state.

Cuprous ion conduction in oxyhalide glasses of the system CuBr-Cu [sub 2] MoO [sub 4]-Cu [sub 3] PO [sub 4]

This paper reports on cuprous ion-conducting glasses, prepared in the pseudo-ternary system CuBr-Cu[sub 2]MoO[sub 4]-Cu[sub 3]PO[sub 4]. These glasses exhibited high ionic conductivities in the range of 10[sup 0] to 10[sup [minus] 3] SM[sup [minus] 1] at room temperature. The infrared spectra showed that these glasses were composed of Cu[sup +], Br[sup [minus]], monomer MoO[sup 2[minus]][sub 4], and monomer PO[sup 3[minus]][sub 4] ions, and were classified as ionic glasses containing one type of cations and three different types of anions. The conductivity of these glasses increased with an increase in the amount of Cu[sup +] ions associated with the CuBr component. Substitution of PO[sup 3[minus]][sub 4] anions for MoO[sup 2[minus]][sub 4] anions caused a decrease in the conductivity of the glasses containing a given CuBr content.

Very Thin Oxide Layer on Fe Surface by Mössbauer Spectroscopy

A thin 57Fe layer (20A) was formed by UHV deposition on the surface of 56Fe film (210A). After exposure to air, Mossbauer and ESCA measurements were carried out. The results show that the oxide layer is fairly uniform with a thickness corresponding to about 12A of Fe, and that the structure is close to γ–Fe2O3. The recoilless fraction of the thin oxide layer does not greatly deviate from the bulk value.

Mössbauer and Structural Studies on (Fe1-xMnx)2B

Mossbauer effect, lattice parameter and thermal expansion measurements were performed in order to obtain the information about the sharp decrease of magnetic moment in (Fe 1- x Mn x ) 2 B with increasing x . The internal field at 0 K (H 0 ) decreases slightly with the increase of x in the composition range x ≤0.33 at a rate of d H 0 /d x ∼-135 kOe. When x becomes larger than 0.33 the slope becomes steeper, d H 0 /d x ∼-450 kOe. These experimental results were explained well by the assumption that the magnetic moment associated with iron atom becomes 0 µ B when iron atoms have more than 7 manganese atoms in its near neighbors. The lattice parameter of a-axis at room temperature varies linearly with composition. On the other hand, in c-axis the lattice-parameter-composition curve shows a kink at x =0.63. No thermal expansion anomaly is observed. This behavior indicates that the magnetic term of lattice parameter remains unchanged even above the Curie temperature.

Preparation of silver ion conducting amorphous materials in the system Ag2S–SiS2 by mechanical milling processes

Silver ion conducting amorphous materials in the system Ag2S–SiS2 were synthesized over the composition range from 0 to 60 mol% Ag2S by use of a high-energy ball-milling process. The electrical and electrochemical properties of the obtained samples were evaluated by using ac impedance spectra, dc polarization measurements, and cyclic voltammetry. These measurements suggested that the silver-ion conductivities of the samples increased with an increase in the Ag2S content and that the activation energy for conduction decreased with an increase in the Ag2S content. The 60Ag2S·40SiS2 (mol%) sample showed its highest ion conductivity, 6.9 × 10−2 S m−1, at 298 K in the system Ag2S–SiS2. This sample also possessed a wide electrochemical window over 2.0 V vs. Ag/Ag+.

Mechano chemical synthesis of a silver ion conductor in the system AgI-Ag3PO4

A high-energy ball-milling process was applied to the preparation of silver ion conductors from the compositions 80AgI 20Ag 3 PO 4 and 60AgI 40Ag 3 PO 4 (mol%); the composition 80AgI 20Ag 3 PO 4 corresponds to that of the crystalline Ag 7 I 4 PO 4 superionic phase, and the composition 60AgI 40Ag 3 PO 4 is reported as a typical composition of the superionic conducting glasses in this system. For the composition 80AgI 20Ag 3 PO 4 , ball milling for longer than 190 h led to the formation of an unknown new crystalline phase, and the new phase showed a high ion conductivity of 6 X 10 -2 S cm -1 at room temperature. The conductivity is higher than that of the crystalline Ag 7 I 4 PO 4 phase. The ball-milling process for the composition 60AgI - 40Ag 3 PO 4 made it amorphous, and the ball-milled sample showed a high ion conductivity very similar to that of melt quenched glass with the same chemical composition.

Effect of calcining temperature on the tetragonal-to-monoclinic phase transition characteristics in 2 mol% yittria-doped zirconia ceramics

Two types of tetragonal-to-monoclinic (t-m) phase transitioncharacteristics were observed in the 2Y-TZP powder samples. In thesample calcined below 1200°C, the t-m phase transitionoccurred below 200°C, and the fraction of the monoclinic phaseincreased sigmoidally. At the beginning of the transition, thefraction of the monoclinic phase increased gradually, and the latticestrain remained unchanged. The abrupt increase in the monoclinicphase accompanying the increase in the lattice strain of thetetragonal phase followed this. Finally, the fraction of themonoclinic phase was saturated, and the lattice strain dropped to0%. The reaction between the adsorbed water and 2Y-TZP was essentialfor the t-m phase transition of 2Y-TZP to occur in air at around roomtemperature. The lattice strain stored in the tetragonal latticeassisted the phase transition. On the other hand, the fraction of themonoclinic phase increased, accompanied by a decrease in the latticestrain in the 1400°C calcined powder. After the fraction ofthe monoclinic phase was almost saturated, the lattice strain droppedto 0%. A gas-solid reaction between the water vapor in air and2Y-TZP and the diffusion of OH− ion into the 2Y-TZP lattice wereessential for this type of t-m phase transition.