Synthesis of Irregular Tantalum Pentoxide (Ta₂O₅) Microparticles by Direct Thermal Oxidation of Ta Foils in Atmospheric Oxygen

In this work, Tantalum pentoxide (Ta₂O₅) microparticles were achieved by one-step thermal oxidation of Tantalum (Ta) foils under 600 °C for 6 h. The effect of time and temperature was explored in the process (50 to 600 °C, 1 to 6 h). Thus, Ta foil was chemically cleaned with nitric and hydrochloric acid and then was immersed in water; finally it was dried with Nitrogen flux. The foils were isothermally oxidized in a horizontal furnace with 21 wt. % Oxygen atmosphere in a constant flux of 20 L/min. The x-ray diffraction, scanning electron microscopy, Raman and energy dispersive x-ray spectroscopy led to the conclusion that formation mechanism of microparticles is mainly constituted by lattice parameters mismatching between Ta and Ta₂O₅ and crystallite size difference. Along the oxidation process at 600 °C, the phase transformation across time carries defect concentrations on entire material experimentally demonstrated by Ta₂O₅ Raman shift and then the sample is broken in irregular shape. As oxidation time reaches 6 h value, phase transformation in Ta foil causes mismatching that firstly diminishes crystallite size, then evolves to cracks and finish by the formation of the particles in the micrometer order size.