All Alkoxide Sol-Gel Route to CoO-TiO2 Nano-Powders

• CoO-TiO2 anatase materials have become highly interesting after the discovery of ferromagnetism above room-temperature, which makes them promising candidates for spintronic devices. There is however still uncertainty, and even contradictory ideas on the origin of the ferromagnetism and detailed microstructures ofthese materials. Here the synthesis and studies of CoO-doped TiO2 nano-phase powders with 0-12 mol% CoO using Co-methoxy-ethoxide and Ti(OPri)4 as precursors is presented. The amorphous precipitates or gels obtained by: (1) air hydrolysis and (2) quench hydrolysis with excess of water were amorphous and completely homogeneous in their Co:Ti ratio. Infrared (IR) spectroscopic and thermo-gravimetric (TG) studies showed that the air-hydrolysed samples Containrd a small amount of methoxy-ethoxide groups, besides coordinated water, while the quench-hydrolysed samples contained large amounts of coordinated water and lacked organic groups. According to the X-ray diffraction (XRD) patterns, the air-hydrolysed samples heated to 600°C contained both anatase and rutile. The rutile formationis ascribed to influence from the residual organic groups. The quench-hydrolysed precipitates yielded phase pure anatase at 480 and 600°C for the 0-6.7 mol% CoO range. At CoO contents of 8-12 mol%, the XRD i studies showed that anatase was obtained at 600°C, but in the 12% case, CoTiO3 was also detected. In addition, the 8-12 mol% samples showed two peaks in the Raman spectrum that might be due to CoO dissolved in anatase at high concentration. The studies were performed with TGA, IR and Raman-spectroscopy, XRD, scanning and transmission electron-microscopes (SEM and TEM, respectively) equipped with energy-dispersive X-ray spectrometers (EDS).

Subject headings

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Keyword

CoO-TiO2

sol-gel

alkoxide route

anatase

spectroscopy

Inorganic chemistry

Oorganisk kemi

Publication and Content Type

ref (subject category)

art (subject category)