This work reports the growth of stable TiO 2 nanotube arrays on flexible Kapton substrates by electrochemical anodization of a sputtered Ti (titanium) film. Although such nanotubes are conventionally fabricated on Ti foils, obtaining these on polymer-based flexible substrates remained a challenge because of higher annealing temperature not compatible with thermal stability of the substrates. Here, we demonstrate the fabrication of TiO 2 nanotubes (1.5 μm long and 80 nm diameter) by anodization of the Ti film deposited using the RF sputtering technique at two different substrate temperatures (room temperature and 300 °C). Nanoindentation and nanoscratch techniques reveal better adhesion of the Ti film with an underlying Kapton substrate for 300 °C deposition temperature. Such investigations reveal a more than twofold enhancement of the "rear pileup" for the Ti film deposited at elevated temperature compared to that at room temperature. The amorphous TiO 2 nanotubes are crystallized at 220 °C for 3 h using a solvothermal technique that allows crystallization at temperatures much lower than the annealing temperature. Application of these nanotubes for photoelectrochemical water splitting reveals a photocurrent density of 18 μA/cm 2 under AM 1.5 G conditions. Furthermore, the charge density and flat band potential (V FB ) are calculated from Mott−Schottky analysis, showing features comparable to the TiO 2 nanotubes on the Ti foil crystallized through thermal annealing. The present work establishes a scalable approach for developing TiO 2 nanotube arrays on the flexible substrate and its use for photo-electrochemical solar energy conversion.
Single-phase polycrystalline Bi[Formula: see text]Ho[Formula: see text]Sm[Formula: see text]FeO3 ceramic is prepared by conventional solid state route. The co-doping of Sm and Ho (via Bi site) in BiFeO3 controls the formation of secondary phases. The Rietveld refinement analysis shows an increasing trend in tilt angle due to the rotation of FeO6 octohedra with respect to host BiFeO3. The remanent polarization and the magnetization of Bi[Formula: see text]Ho[Formula: see text]Sm[Formula: see text]FeO3 ceramic are found to be significantly improved than BiFeO3 and Bi[Formula: see text]Sm[Formula: see text]FeO3 at room-temperature. Considerable variations in the remanent polarization (0.18 to 0.11 [Formula: see text]C/cm2) on magnetic poling and a dielectric anomaly in the vicinity of the antiferromagnetic transition temperature are due to the intrinsic magnetoelectric coupling effect in Bi[Formula: see text]Ho[Formula: see text]Sm[Formula: see text]FeO3 ceramic. The dielectric permittivity increases with increase in applied magnetic field and the coupling coefficient of Bi[Formula: see text]Ho[Formula: see text]Sm[Formula: see text]FeO3 ceramic is found to be 0.91% at 4 kOe.
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