Photoanodic Properties of Plasma Sprayed TiO_2 Coatings(Surface Processing)

概要

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Plasma spraying has been used to prepare n-type polycrystalline TiO_2 coatings on titanium substrate as photoanodes. The photoanodic properities of plasma sprayed TiO_2 coatings depend on the extent of oxygen loss and impurity of TiO_2 particles during plasma spraying. These properties depending on plasma conditions, additives and heat treatment are elucidated in oxygen saturated solution of 0.1 N NaOH. It is shown that the plasma spray atmosphere and plasma auxiliary gas, hydrogen, influence greatly the photoanodic properties of TiO_2 coatings. Moreover, the photoanodic current increases by heat treatment (400℃-90min) in air and by addition of Y_2O_3 to TiO_2 coatings. Bandgap (BG) and subbandgap (SBG) photocurrent transients of TiO_2 coatings electrode were explored as a function of the external applied bias and light wavelength. These photocurrent transients disappear at high anodic potentials and increase at high cathodic potentials. Kinetic response of an anodic photocurrent which shows spike immediately and again increases with time after the light is turned on for plasma sprayed TiO_2 coatings, has been discussed with impurity center.
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