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The average structure and microstructure of a lithium-ion conducting perovskite La2/3−xLi3xTiO3 (x = 0.12) were investigated using neutron diffraction and transmission electron microscopy (TEM). The obtained results were compared with those of previous studies on La2/3−xLi3xTiO3 series compounds, and the relationship between their structures and ionic conduction was discussed. The Rietveld refinement using neutron diffraction data reveals that the average structure (space group: Cmmm) of furnace-cooled Li-rich La2/3−xLi3xTiO3 (x = 0.12) involves alternative ordered arrangement of La along the c-axis and anti-phase-tilt of TiO6 octahedra along the b-axis as with Li-poor La2/3−xLi3xTiO3(x = 0.05). It was found that the strong correlation between structure and percolative diffusion pathways in the perovskites is primarily referred to the ordered arrangement of La ions, and the “bottleneck” square—surrounded by four oxygen ions determined by the distortion and tilt of TiO6 octahedra. In addition, the 90°-oriented micro-domain structure, which also influences the percolative diffusion pathways in La2/3−xLi3xTiO3, was observed by TEM.

The recovery of lithium ions by electrolysis using lithium ion conductive perovskite-type oxides La2/3−xLi3x□1/3−2xTiO3, as a separator, has been carried out. It was confirmed that La2/3−xLi3x□1/3−2xTiO3 has the selective permeability for lithium ions, and La2/3−xLi3x□1/3−2xTiO3 can be applied to the electrochemical recovery for lithium ions. Moreover, 6Li ion was recovered in preference to 7Li ion by this electrolysis. This indicates the possibility of isotope separation for the lithium, 6Li and 7Li.

We have prepared new perovskite-type lithium ion conductors, La x M y Li 1−3 x − y NbO 3 (M=Ag and Na) and investigated the lithium ion conductivity in these compounds. Maximum lithium ion conductivity at 300 K was found to be 3.9×10 −5 S⋅cm −1 for La 0.25 Ag 0.20 Li 0.05 NbO 3 , which contain the minimum amount of Li ion among these compounds. This result indicates that the Li ion conductivity of these compounds is mainly dominated by the activation energy. The reason for low ionic conductivities of these compounds is that the lattice parameters are not sufficiently optimized for Li ion conduction in the perovskite niobate.

The oxygen content of rare earth manganates La 0.5 Ca 0.5 MnO 3 , Pr 0.5 Ca 0.5 MnO 3 , Pr 0.5 Sr 0.5 MnO 3 and Nd 0.5 Sr 0.5 MnO 3 with different degrees of charge ordering instabilities is varied by controlled annealing in N 2 . The oxygen deficiency increases the unit cell volume and decreases the tolerance factor. The electron transport and magnetic properties are sensitive to the deviation of the %Mn 4+ variation of tolerance factor of the oxygen deficient charge ordered manganates from that of the oxygen stoichiometric manganates with same A-site ions and different 〈 r A 〉. Pr 0.5 Sr 0.5 MnO 3 and Nd 0.5 Sr 0.5 MnO 3 with larger deviations show different behavior while La 0.5 Ca 0.5 MnO 3 and Pr 0.5 Ca 0.5 MnO 3 with smaller deviations follow the behavior expected from the decreasing Mn 4+ concentration. Oxygen deficiency broadens the Mn 4+ concentration range of charge ordering instability in the former and suppresses in the latter. Apart from the crystal structure deformations the oxygen defects modify the electronic band structure in a complex manner.

High-temperature quantum paraelectricity in perovskite titanate series (Ln 1/2 Na 1/2 )TiO 3 has been investigated in relation to their structural deformation for Ln 3+ -substitutions, Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Except for Ln=La and Ce, (Ln 1/2 Na 1/2 )TiO 3 has an orthorhombic unit cell with space group Pnma. The essential deformation parameter which lowers the highest dielectric constant e a at the quantum paraelectric state, is found to be the average tilt angle δ among the neighboring [TiO 6 ]-octahedra for (Ln 1/2 Na 1/2 )TiO 3 . e a decreases moderately as a function of cos( δ /2) for less than half-filled Ln 3+ -range, however, it decreases sharply for more than half-filled Ln 3+ -range. Supposing a virtual spontaneous polarization P s with a virtual ferroelectric transition temperature T 0 , and a zero-point vibrational energy h v 0 /2 of Ti 4+ -oscillators in [TiO 6 ]-octahedra, a condition for the appearance of quantum paraelectricity in perovskite titanates is given by T 0 T *∼ h v 0 /2 k , where T * is the cross-over temperature from classical to quantum regime. By analogy with the simple harmonic oscillator, the width of the potential on the Ti 4+ ions in [TiO 6 ]-octahedra determines their zero-point energy h v 0 /2, which is considered as the quantum fluctuation energy, replaces the thermal fluctuation energy k T below the cross-over temperature T *. The fundamental frequency v 0 of the Ti 4+ -oscillator is characteristic of the materials, that is, the narrower the potential is, the higher the v 0 is. Therefore, the structural deformations through the tilts or shrinks of the [TiO 6 ]-octahedra cause to the high-temperature quantum paraelectricity in the perovskite titanates via increase in v 0 , T * and T a , the arrival temperature at the quantum paraelectric state.

We have executed the molecular dynamics (MD) simulation in SrTiO 3 using the partially ionic model (PIM), and optimized the relevant potential parameters except for the effective charge of each ion. The room temperature crystal structure, the thermal expansion and the compressibility of SrTiO 3 were found to be reproducible by MD simulation using PIM.

The novel perovskite-type oxides (Ln 1/2 Na 1/2 )TiO 3 (Ln = Dy, Ho, Er, Tm, Yb, Lu) were synthesized, and their crystal structures and dielectric properties were examined. (Ln 1/2 Na 1/2 )TiO 3 (Ln = Dy, Ho, Er, Tm, Yb, Lu) possess an orthorhombic symmetry with space group Pnma similar to (Ln 1/2 Na 1/2 )TiO 3 (Ln = Pr, Nd, Sm, Eu, Gd and Tb). Their lattice parameters and dielectric constants decrease with an increase in the atomic number of Ln (Ln = Dy to Lu). At low temperatures, (Ln 1/2 Na 1/2 )TiO 3 (Ln = Dy, Ho, Er, Tm, Yb, Lu) shows quantum paraelectric behavior.

By refining the etching technique and subsequent graphic processing, the contiguity, relative alignment and thickness of grains in Ag-sheathed Bi(2223) tape were evaluated from a cross-sectional electron micrograph. Graphic processing was achieved by digitization, inversion and skeletonization of each grain, followed by a description of the two-dimensional distribution of the three-forked crossings (`switches') and the grain thickness. A simple quasi-linear relation between the switch density and the critical current density, J C , was observed, indicating the significance of the grain contiguity.

Hydrostatic pressure effects on resistivity and Neel temperature of B site 1:1 ordered perovskite oxide Ba 2 (FeMo)O 6− δ with oxygen deficiency δ ≈0.1 were studied up to 13 kbar. The sample has a Neel temperature of 282 K, which increases linearly with pressure at a rate of 1.69 K kbar −1 . The resistivity of the sample is low and shows metal-like behavior. Under applied pressure, the resistivity is depressed. The above results show similar trends as in the case of chemical pressure.

In order to attain a higher lithium ion conductivity in perovskite-type oxide the effect of elemental substitution was investigated for solid solution systems (1-x)La 0.55 Li 0.35 TiO 3 -xKNbO 3 , (1-x)La 0.55 Li 0.35 TiO 3 -xKTaO 3 and La 0.55 Li 0.35-x K 3 TiO 3 . The results were explained by considering the effects of lattice expansion, site percolation and local distortion of the lattice.

The influence of carrier (lithium and vacancy) concentration on the lithium ion conductivity in perovskite-type oxides La 2 3 − x Li 3x □ 1 3 − 2x TiO 3 and yLa 0.5 Na 0.5 TiO 3 −(1 − y ) La 0.55 Li 0.35 □ 0.1 TiO 3 solid solutions has been investigated from the view of percolation theory. Consequently, the ratio of lithium to vacancy concentration and site percolation were found to be predominant factors in lithium ion conductivity of perovskite-type oxides.

Lithium was electrochemically inserted into perovskite oxides, SrVO 3 − δ , La 2 3 TiO 3 − δ and (La, Li)TiO 3 − δ , by using a galvanic cell: Li ¦1M LiClO 4 in PC ¦perovskite oxide. The tetravalent transition metal ion (Ti, V) can be reduced to the minimum valence of 3 by lithium insertion. This fact was explained by the effect of valence on the lattice self-potential and site-potential in the ideal perovskite oxide ABO 3 . We tried to explain the lithium insertion and high lithium conductivity in the perovskite oxide from the view point of electrostatic potentials.

The lithium ion conductivity in the perovskite-type xLiTa0 3 -(1 - x)SrTiO 3 solid solution (0.30 ≤ x ≤ 0.50) has been investigated. The highest ionic conductivity of 5.5 X 10 -4 S cm -1 at 300 K appears at x = 0.50. The ion conductivity decreases with a decrease in x and then rapidly decreases in the vicinity of x = 0.30. This threshold for the ion conductivity is the same as the site percolation threshold for a simple cubic lattice. This indicates that the lithium ion conduction occurs three-dimensionally among the A-sites of the perovskite.

Perovskite-type compounds La0.51(1)Li0.34(1)TiO2.94(2), Pr0.56(2)Li0.34(2)TiO3.01(3), Nd0.55(2)Li0.34(1)TiO3.00(3), and Sm0.52(1)- Li0.38(1)TiO2.97(2) were synthesized and their structures and lithium ion conductivities were investigated. Symmetry of the lattice changes from cubic for La0.51(1)Li0.34(1)TiO2.94(2) to orthombic (space group: Pmmm) for Pr0.56(2)Li0.34(2)TiO3.01(3) and Nd0.55(2)Li0.34(1)TiO3.00(3), and to orthorhombic (Pmma or Pnma)for Sm0.52(1)Li0.38(1)TiO2.97(2). Lithium ion conductivities decrease with decreasing the radii of lanthanide ions, which play the role of spacer for lithium ions.

Compounds with perovskite structure which were candidates for high ionic conductivity were searched and synthesized on the basis of the knowledge of lanthanum lithium titanates and their ionic conductivity was investigated. The free volume for lithium ions to migrate, and the lithium and vacancy concentrations on the A-site play important roles for the ionic conductivity in the perovskite structure. Lanthanum lithium titanate substituted with 5 mol% Sr had a larger free volume and showed higher ionic conductivity of the bulk part ( σ =1.5×10 −3 S cm −1 at 300 K) than the pure lanthanum lithium titanate.

Lithium was electrochemically inserted into SrVO3−δ by using a galvanic cell: Li|1M LiClO4 in PC|SrVO3−δ. After the insertion of the amount x=0.1 in LixSrVO3−δ, metallic conductivity was maintained being accompanied by an increase of the absolute value of one order of magnitude and a very small volume increase was observed. The results indicate the possibility to use SrVO3−δ as a cathode without any conductive additives in rechargeable lithium batteries.

A new oxygen-deficient and ordered perovskite-type solid-solution system Ba 1+ x Bi 1- x O y (O⩽ x ⩽0.5, 3.00⩾ y ⩾2.75) was synthesized, with the estimated ionic configuration Ba 2+ x Bi .3+ 3.5−1.5 x − n Bi .5+ −3+0.5 x+y Bi 5+ 0.5 )O y . The lattice parameters and mean valence of bismuth in the sample annealed in one atmosphere of oxygen at 673 K were determined by powder X-ray diffraction and iodemetric titration, respectively. Samples with the compositions 0⩽ x ⩽0.05, 0.10⩽ y ⩽0.15, 0.20⩽x⩽0.425, 0.45⩽x⩽0.475, and 0.475⩽x⩽0.50 were found to be monoclinic, rhombohedral, cubic, tetragonal and cubic, respectively. Oxygen deficiency was observed in the whole range of composition; the ordering of the oxygen vacancies was confirmed for x ⩾0.45. Oxygen deficiency at high temperatures was measured by P 02 -controlled thermogravimetry for samples with the compositions, x =0.33 and 0.50 and within the ranges of 873⩽T⩽1313 K and 0.001⩽P 02 ⩽1 atm. At least four phases were recognized in the phase diagram for the sample x =0.33 in the measured range of the temperature and oxygen partial pressure, while no phase change was observed for the sample x =0.50.

The ion-exchange reaction between β″-alumina and solid α-AgI was investigated by measuring the EMF of a galvanic cell with a β″-alumina solid electrolyte. The following cell was assembled and EMF measurements were taken in a temperature range between 342 to 816 K : Mo , Na(s, 1)| β ″-alumina|Ag+AgI+ β ″-alumina, Mo (I). Ag, AgI and β″- alumina powders were mixed in a molar ratio of Ag : AgI : Na (in β″-alumina powder) of 1.00 : 1.00 : 1.00. The cell was heated and maintained at 630 K for 30 d. The ion-exchange between Ag + ion in α-AgI and Na + ion in β″-alumina powder gradually proceeded and formed two solid solutions of (Ag + −Na + )I − and (Na + −Ag + )-β″-alumina. The resulting EMF was higher than that of cell ( II ) : Mo , Na(s, 1)| β ″-alumina|NaI+Ag+AgI, Mo(II). The 30 days retention at 630 K gave a cell EMF of 2.1370 V which was higher than the EMF of cell (II) by 9.6 mV. When the cell temperature was decreased below 600 K, a NaI saturated with AgI, (Na + −Ag + )I − sat. phase appeared and the EMFs of cell (I) agreed with the EMFs of cell (II). By heating the cell to a particular temperature on the liquidus line on the AgI side of the AgINaI system, a liquid phase appeared and the ion-exchange between α-AgI and β″-alumina smoothly proceeded via the liquid. After that, two kinds of three-phase-equilibria of (Ag −Na−I ) sat. +(Ag + −Na + )I − sat. +(Na + −Ag + )I − sat. and (Ag −Na−I ) sat. + (Ag + −Na + )I − sat. +liquid (Ag + −Na + )I − were attained below and above 657 K, respectively. Then, the EMFs of cell (I) agreed with the value of cell (II) below 657 K.