Gin-ya Adachi

Ionic Conductivity of Solid Electrolytes Based on Lithium Titanium Phosphate

Solid electrolytes based on lithium titanium phosphate were prepared, and their phase, porosity of the sintered pellets, and electrical conductivity were studied. The conductivity was increased and the porosity decreased greatly by partially replacing Ti4+ and P5+ in with M3+ and Si4+ions, respectively. The maximum conductivity at 298 K is for . The conductivity was considerably increased by the mixing of binders such as or with . The main reason for the conductivity enhancement of these electrolytes seems to be attributable to the increase of the sintered pellet density with the enhancement of the lithium concentration at the grain boundaries.

Ionic conductivity of the lithium titanium phosphate (Li/sub 1+x/M/sub x/Ti/sub 2-x/(PO/sub 4/)/sub 3/, M=Al, Sc, Y, and La) systems

High lithium ionic conductivity was obtained in Li/sub 1+X/M/sub X/Ti/sub 2-X/(PO/sub 4/)/sub 3/ (M=Al, Sc, Y, and La) systems. Lithium titanium phosphate, LiTi/sub 2/(PO/sub 4/)/sub 3/, is composed of both TiO/sub 6/ octahedra and PO/sub 4/ tetrahedra, which are linked by corners to form a three dimensional network, with a space group R3-barC. Some workers have already described that the conductivity increased considerably if Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ was substituted by slightly larger cations such as Ga/sup 3+/(1),Sc/sup 3+/(2), and In/sup 3+/(3,4). These results are similar to each other because of their close ionic radii. In this communication, substitution effects of Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ by various ions (Al/sup 3+/, Sc/sup 3+/, Y/sup 3+/, and La/sup 3+/) on their conductivities are reported.

Electrical property and sinterability of LiTi2(PO4)3 mixed with lithium salt (Li3PO4 or Li3BO3)

Abstract A lithium salt (Li 3 PO 4 or Li 3 BO 3 ) was added to LiTi 2 (PO 4 ) 3 to obtain a dense pellet of the phosphate. The porosity of the sintered pellets decreased and the conductivity was enhanced by the utilization of a binder. A maximum conductivity of 3.0 × 10 −4 S·cm −1 at 298 K was obtained for a sample of LiTi 2 (PO 4 ) 3 −0.2Li 3 BO 3 . The activation energy for the lithium migration at grain boundaries was decreased by the addition of lithium salt. The reason for the conductivity enhancement was attributed to a decrease in the activation energy for the lithium migration at the grain boundary and an increase in the contact area between grains. The conductivity of the bulk component was also increased by the enhancement of Li + -ion migration at grain boundaries.

Ionic conductivity and sinterability of lithium titanium phosphate system

Abstract Lithium titanium phosphates mixed with various metal ions of M 3+ (M=Al, Cr, Ga, Fe, Sc, In, Lu, Y, or La), Li 1+ x M x Ti 2− x (PO 4 ) 3 systems, were prepared, and their properties were investigated. The conductiv ity was enhanced and the porosity of the sintered pellets decreased by the partial replacement of Ti 4+ with the M 3+ ion. The porosity was considerably influenced by the ionic radius of the M 3+ ion. The sinterability was greatly related to the increase of lithium concentrations at the grain boundary. The conductivity enhancement by the substitution mainly resulted from the densification of the sintered pellets.

The Electrical Properties of Ceramic Electrolytes for LiM x Ti2 − x ( PO 4 ) 3 + yLi2 O , M = Ge , Sn , Hf , and Zr Systems

The electrical properties of systems of , were examined in detail. The conductivity and the sinterability increased with the amount of excess lithium oxide in the phosphate. The secondary phase acts as a flux to accelerate the sintering process and to obtain high conductivity grain boundaries. The conductivity decreased and the activation energy of the bulk component for Li+ migration increased by the partial substitution of Tr4+for M4+ in systems of . A minimum activation energy of 0.28–0.30 eV, was obtained for the sample with ca. 1310 A3 in the cell volume. has the most suitable tunnel size for a Li+ migration through the NASICON‐type network structure.

Preparation of ceria–zirconia sub-catalysts for automotive exhaust cleaning

This paper focuses on the development of ceria–zirconia materials which have high thermal stability and high catalytic activity. The CeO2–ZrO2 system is very important as a sub-catalyst in the autoexhaust catalytic converters, especially on the oxygen-storage capacity (OSC). The role of the CeO2–ZrO2 is to adjust the air–fuel ratio to the stoichiometric value to attain the simultaneous conversions of the three main pollutants such as CO, NOx and hydrocarbons, by providing and absorbing oxygen during fuel-rich and fuel-lean conditions, respectively. In this article, recent advances in the design and development of the sub-catalysts in the autoexhaust catalytic converters are reviewed.

Luminescence properties of Eu(II)-borates and Eu2+- activated Sr-Borates

Abstract The luminescence properties of Eu(II)-borates and Eu 2+ -activated Sr-borates were studied, e.g. Sr 1− x Eu x B 2 O 4 Sr 1− x Eu x B 4 O 7 and Sr 1− x Eu x B 6 O 10 . It was found that Sr 1− x Eu x B 4 O 7 consisting of a three-dimensional network of BO 4 tetrahedra gave a remarkably stronger emission than the other compound consisting of BO 3- 3 ions, B 2 O 4- 5 ions, (BO 2 )∞ chains or a (B 3 O 5 )∞ network. This was understood by considering their crystallographic properties and with help of the Dexter theory.

Recovery of rare metals from scrap of rare earth intermetallic material by chemical vapour transport

Abstract A dry process for recovery of rare metals from sludges of Sm 2 Co 17 , Nd 2 Fe 14 B and LaNi 5 intermetallic compounds was investigated using chemical vapour transport along a given temperature gradient. Chlorine and aluminium chloride were used as a chlorinating agent and a transporting agent respectively, and the rare metal chlorides were chemically transported as vapour complexes, e.g. RAl n Cl 3+3 n (R = rare earth), Mal n Cl 2+3 n (M = Co, Ni). Rare earth chlorides were concentrated in the deposits in the higher temperature zone (800–900 °C) while cobalt and nickel chlorides were in the lower temperature zone (500–700 °C). Purity of each of the recovered chlorides was more than 99%. Chlorides of other metals, such as iron, copper, zirconium, and aluminium, were condensed at the outlet of the reactor (below 350 °C) without any contamination for the recoveries. After transport reaction for 6 h, yields of nickel and cobalt were more than 99%, whereas those of lanthanum, samarium, neodymium and dysprosium were lower, i.e. 27%, 39%, 59% and 68%, owing to the relatively low formation rate of RAl n Cl 3+3 n complexes. If the transport reaction lasts for a longer time, the yields of rare earths can be improved.

Electrical properties and crystal structure of solid electrolyte based on lithium hafnium phosphate LiHf2(PO4)3

Abstract The electrical properties and the crystal structure were investigated for the ceramic electrolytes based on LiHf 2 (PO 4 ) 3 . The conductivity enhanced by the Li 2 O addition with LiHf 2 (PO 4 ) 3 system and by the increase of x for Li 1+ x M x Hf 2− x (PO 4 ) 3 (M=Cr, Fe, Sc, In, Lu or Y) systems. The P2 1 /n monoclinic phase transformed to NASICON-type R 3 c rhombohedral phase at above 1173 K. The activation energy for Li + ion migration was decreased by the phase transition. The activation energy for bulk component was 0.42 eV for the NASICON-type structure. A maximum conductivity at 298 K is 1.7 × 10 −4 S·cm −1 for the sample of Li 1.2 Fe 0.2 Hf 1.8 (PO 4 ) 3 .

Luminescence properties of lanthanide complexes incorporated into sol-gel derived inorganic-organic composite materials

Abstract Lanthanide complexes such as [Tb(bpy) 2 ]Cl 3 and [Eu(phen) 2 ]Cl 3 incorporated into the organically modified silicates (ormosil) were prepared and their luminescence properties measured. The ormosil composite materials incorporated with [Tb(bpy) 2 ]Cl 3 and [Eu(phen) 2 ]Cl 3 had green and red emissions and, by optimization of the complex concentration amounts and heat treatment conditions, they provided emission intensities with 100 and 80%, respectively, of those for conventional phosphors used as lamp illumination. The resulting composite materials also possessed excellent mechanical strength, hydrolytic stability, and, consequently good durability for the emissions from the lanthanide compositions after being exposed to laboratory atmosphere for 100 days.