S. Yoshikado

The crystal structure of tetragonal form PbSnF4

Abstract We carried out single crystal X-ray diffraction measurement of tetragonal form PbSnF4: a=4.215 (3) A , c=11.744 (32) A , V=208.6 (5) A 3 , space group P4/nmm, z=2, and Dcalc=6.26 g/cm3. The structure was refined to wR=0.031 by the least-squares methods, using 132 reflections. The compound has the order arrangement of Pb and Sn metals constructing the sequence of …PbPbSnSnPbPb… along the c-axis direction. The fluorine ions in M2(Sn) cube were disordered in distorted tetrahedra. It is considerable that the disordered ions are related with the high ionic conductivity in PbSnF4.

Variable-temperature X-ray diffraction analysis of the behavior of the mobile fluorine ions in a superionic conductor, β-PbF2

Abstract We carried out single-crystal X-ray diffraction measurements of β-PbF 2 (quenched from 970 K) in the temperature range 131 to 298 K. The structure was refined to R = 0.008 at 131 K and R = 0.008 at 298 K by the least-squares methods, using about 80 reflections. The behavior of the one independent mobile fluorine ion could not be attributed to split atoms but instead was due to anharmonic thermal vibration.

Ion conduction in one-dimensional ionic conductors A1−xTi2+xB5−xO12(ATBO, ANa or K and BAl or Ga), x<1)

Ion conduction in one-dimensional alkali ionic conductors A1−xTi2+xB5−xO12(x<1) (ATBO, e.g. NTAO for ANa and BAl and KTGO for AK and BGa) has been studied in the frequency region between 100 Hz and 32.55 GHz. KTGO is a newly synthesized material. It is isostructural with NTAO which has been determined by another worker. Both the frequency-dependent and frequency-independent high ionic conductivities have been observed. The frequency dependence of the complex conductivity was almost the same as that of KMg-priderite with hollandite-type structure due to the existence of bottlenecks in tunnels; it was analyzed by Bernasconis random barrier model. Analytical results show that the attempt frequency may be dominated by the coupling of the vibration of mobile ions with the lattice vibration (Au mode) of the tunnel framework. The frequency independent ionic conductivity was thermally activated and the activation energy was 0.27 eV for NTAO and KTGO.

NMR study of one-dimensional ionic conductor with hollandite-type structure. II. Frequency dependence of spin-lattice relaxation time of 27Al

Abstract Frequency dependence of spin-lattice relaxation time T 1 of 27 Al in one-dimensional K + ion conductor, K-Al-priderite, was measured at 45 K in the frequency range from 10.1 MHz to 55 MHz. It is found that T 1 is proportional to ω 1.49±0.05 and agrres well with the ω 3 4 dependence derived by the continuum diffusion model. The intrinsic activation energy is determined to be 0.058 eV by doubling the slope E NMR =0.029 eV of the d(ln T 1 )/d T curve in the low temperature region. The frequency dependence of T 1 in the high temperature region measured in the frequency range from 11.5 MHz to 20.8 MHz shows a tendency that the frequency dependence becomes smaller than the ω 1 2 dependence as temperature is raised above 450 K.

Ionic conduction and crystal structure of β-Pb1−xSnxF2 (x≤0.3)

Abstract The crystal structures of β-Pb 0.9 Sn 0.1 F 2 (Sn10) and β-Pb 0.8 Sn 0.2 F 2 (Sn20) were determined using single crystal intensity data on a four-circle diffractometer. The structures have cubic symmetry; the lattice parameters: a =5.946(1) A, V =210.2(2) A 3 , space group Fm3m (No. 225) for Sn10 and a =5.957(1) A, V =211.4(1) A 3 , space group Fm3m (No. 225) for Sn20. The structures were refined to w R =4.2% for Sn10 and 3.6% for Sn20 by the least-squares method, using 76 unique reflections with | F 0 |>3 σ (| F 0 |). The fluorine ions are statistically distributed in 32 sites of (0.25+ δ , 0.25+ δ , 0.25+ δ ). δ , displacement from the normal fluorine site, increases with the SnF 2 content. The isotropic temperature factor of the fluorine, B iso =16.5(2.3) A 2 , for Sn20, is very large compared with that for Sn10 ( B iso =3.18(45) A 2 ). Ionic conductivity in this system increases with the magnitude of the temperature factor of the fluoride ion.

Ionic conduction of new one-dimensional ionic conductors with large tunnels: Ax[Ga8Ga8+xTi16−xO56] (A=K, Rb, OR Cs, x≤2)

Ionic conduction in new one-dimensional (1-D) alkaline ionic conductors A x [Ga 8 Ga 8+ x Ti 16− x O 56 ] (AGGTO, A=K, Rb and Cs, x≤2 ) is studied by measuring the complex ionic conductivity between 100 Hz and 32.55 GHz. AGGTO has a tunnel structure with a smooth inside wall lacking bottlenecks . In the low-frequency region, the real and imaginary parts of the complex ionic conductivity indicate the dispersion due to the blocking effects by large impurity ions in tunnels on the motion of mobile ions. In the high-frequency region, the ionic conductivities at room temperature are large (e.g. ≈8 S/cm for RGGTO). Negative values of the dieletric constants for RGGTO and CGGTO are observed at microwave frequencies. The results show that ionic conduction in the microwave frequency region is dominated by collisions between mobile ions in the same tunnel. The ionic conduction in AGGTO can be explained in terms of the classical ion transport model.

Crystal structure of beta-lead fluoride doped potassium fluoride and ionic conduction

Abstract Structural studies and ionic conductivity measurements have been carried out on a single crystal of β-Pb 0.9 K 0.1 F 1.9 , which was synthesized using a dry method. The crystal is cubic: a ==5.941 (1) A, space group, Fm3m, z =4. The structure was refined to R =0.025 by least-square methods, using 83 unique observed reflections. The conductivity of this material is σT =1.4 (S cm −1 K) at 300 K and the activation energy 0.24 eV. From these results it appears that the fluorine vacancies may be considered to be predominant mobile species in the extrinsic region. The phase is one of the best fluorine ion conductors.

Relation between x-ray emission mechanism and crystal structure in LiNbO3

x-ray emission in LiNbO3 is confirmed by thermal treatments in a vacuum system by a new cleaning method of the crystal. Detailed single-crystal high-temperature x-ray structure refinements were carried out at 297, 323, 373, 423 and 473 K, far below the phase transition (~1473 K). The unit cell dimensions a and V show a linear increase with temperature; however, the lattice parameter, c shows only a slight linear increase. The length of Nb–O bonds in adjacent octahedra is almost constant below 423 K. It is suggested that the valence electron in Nb changes in the compound. Therefore, x-ray emission induced by charged particles including electrons can be considered to have a close relation to the electric charge of Nb in LiNbO3.

NMR study of one-dimensional ionic conductor with hollandite-type structure iv) Rb-priderite

Abstract Conduction properties of Rb + ion in Rb-Al-priderite, Rb 1.49 Al 1.65 Ti 6.35 O 15.92 , and K + ion and Rb + ion in (K,Rb)-Al-priderite, K 0.83 Rb 0.68 Al 1.73 Ti 6.23 O 15.89 , were investigated by NMR using 27 Al in the framework as a probe. Size effect was observed remarkably in the activation energies. Frequency dependence of T 1 in Rb-Al-priderite at a low temperature is T 1 ∞ ω 1.53±0.09 , indicating that the relaxation behavior of 27 Al in Rb-Al-priderite is also described by the continuum model. Barrier height distributions and “attempt frequencies” in both samples obtained by a curve-fitting method are discussed in comparison with those of K-Al-priderite.

Fabrication of Al2O3 Films Using Aerosol Deposition Method and Their Characterization

An aerosol deposition method (ADM) apparatus is newly designed and fabricated. Heat-dried-alumina (Al2O3) particles of an average diameter of ~500 nm with narrow dispersion were used as starting materials. These were mixed with N2 carrier gas, and formed a colloiding aerosol. These were accelerated to several hundred m/s through a fixed narrow slit nozzle, and ejected to the substrate. The Al2O3 film was deposited by scanning the substrate with 125 μm/s at room temperature. The deposited Al2O3 films were highly transparent. It is confirmed that there was no primary but crushed particles in the film. Roughness of thin film with 1 μm thick was approximately 22 nm. It is expected that highly dense Al2O3 films could be deposited. Deposition on other materials is also available at room temperature.