Tantalum oxide gels in the form of transparent monoliths and powders have been prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)(5):C2H5OH:H2O:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, the time of gel formation increased with the alcohol to alkoxide molar ratio. Thermal evolution of the physical and structural changes in the gel has been monitored by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, and infrared spectroscopy. On heating to similar to 400 degrees C, the amorphous gel crystallized into the low-temperature orthorhombic phase beta-Ta2O5, which transformed into the high-temperature tetragonal phase alpha-Ta2O5 when further heated to similar to 1450 degrees C. The volume fraction of the crystalline phase increased with the firing temperature. The alpha-Ta2O5 converted back into the low-temperature phase, beta-Ta2O5, on slow cooling through the transformation temperature of 1360 degrees C, indicating a slow but reversible transformation.