High-temperature X-rays diffractometry is used to study Ti₂O₃ rhombohedral oxide formed by reduction of titanium dioxide, under vacuum and in the presence of graphite or metallic titanium. The sesquioxide is charac- terrized by a homogeneous field of very low oxygen pressure, both boundary phase appearing independently from one another between 800 and 1715°C. The c/a = 2.660 value for Ti_2-xO₃ oxidized from of the equivalent hexagonal cell reaches c/a = 2.735 for Ti₂O₃ reduced form, which does not undergo quenching (c/a = 2.640 at room temperature)