3.3.1 Effect of excessive Mg

The influence of excessive Mg [33] to produce higher-purity MT was investigated further by XRD for samples which were calcined at 800°C [29]. It has been shown that excessive addition of Mg up to 3% reduces the amount of rutile (R), while above 6% addition causes vanishing rutile but the appearance of periclase (M). This result implies that the method can be easily used to control the amount of MT by varying Mg:Ti ratio without the introduction of MgTi2O5 or Mg2TiO4 which was found when other methods were used [30, 32]. The results explained the role of excessive Mg in the formation of high-purity MT. The amount of MT can achieve as high as 99.4 3.6% in the 6% excessive Mg sample with rutile as the sole residual or 97.5 3.5% in the 3% excessive Mg sample with periclase as also the only residual. An excessive Mg around 5–6% is therefore envisaged to give MT with the highest purity [29].
