Textured bulk ceramics have been prepared of various cobaltites including the common CdI 2 -type CoO 2 layer (i.e., [Ca 2 (Co 0.65 Cu 0.35 ) 2 O 4 ] 0.624 [CoO 2 ]: CCO-4-layer, [Bi 2 M 22x O 4 ] p [CoO 2 ] (M 2 ~Sr 2 : BSCO, M 2 ~Ca 1 Sr 1 : B(SC)CO, M 2 ~Ca 2 : BCCO)) by using b-Co(OH) 2 (CdI 2 -type) platelets as reactive templates, and their thermoelectric (TE) properties have been examined. All the specimens were found to be highly c-axis aligned ceramics. Especially for CCO-4-layer, B(SC)CO and BCCO, the present study is the first report on the fabrication of textured ceramics. Our textured ceramic specimens exhibited larger values of electrical conductivity (s) than the ceramics prepared by a conventional solid-state reaction (SSR specimens): e.g., s ab ~0.46 6 10 4 S m 21 for the textured specimen and s SSR ~y0.26 6 10 4 S m 21 at 1060 K for the SSR specimen for BCCO. This study indicated that our preparation method using b-Co(OH) 2 templates is a versatile and effective technique to fabricate cobaltites, including CoO 2 layers, with a high degree of orientation and improved TE properties.

We improve the surface of graphene by atomic layer deposition (ALD) without the assistance of a transition layer or surface functionalization. By controlling gas-solid physical adsorption between water molecules and graphene through the optimization of pre-H2O treatment and two-step temperature growth, we directly grew uniform and compact Al2O3 films onto graphene by ALD. Al2O3 films, deposited with 4-cycle pre-H2O treatment and 100-200 °C two-step growing process, presented a relative permittivity of 7.2 and a breakdown critical electrical field of 9 MV/cm. Moreover, the deposition of Al2O3 did not introduce any detective defects or disorders in graphene.

A positive muon spin rotation and relaxation (µ + SR) experiment on [Ca2CoO3]0.62[CoO2], (i.e., Ca3Co4O9, a layered thermoelectric cobaltite) indicates the existence of two magnetic transitions at ∼ 100 K and 400 -600 K; the former is a transition from a paramagnetic state to an incommensurate (IC) spin density wave (SDW) state. The anisotropic behavior of zero-field µ + SR spectra at 5 K suggests that the IC-SDW propagates in the a-b plane, with oscillating moments directed along the c-axis; also the IC-SDW is found to exist not in the [Ca2CoO3] subsystem but in the [CoO2] subsystem. In addition, it is found that the long-range IC-SDW order completes below ∼ 30 K, whereas the short-range order appears below 100 K. The latter transition is interpreted as a gradual change in the spin state of Co ions above 400 K. These two magnetic transitions detected by µ + SR are found to correlate closely with the transport properties of [Ca2CoO3]0.62 [CoO2].