Preparation of BaTiO3 single crystals using the modified SiO2-exaggerated grain growth method

BaTiO3 single crystals were prepared by a modified exaggerated grain growth method with SiO2 additions using commercially available BaTiO3 powder (BaO/TiO2=0.987) in place of high purity (BaO/TiO2=0.999) expensive BaTiO3 powders. The modification also involves dropping of a eutectic composition of SiO2 and BaTiO3 in place of pure SiO2 on the green sample of BaTiO3. Doing this, a complex system involving the two eutectics-one between BaTiO3 and SiO2 at 1260 °C and another between BaTiO3 and TiO2 at 1320 °C was identified. Controlling the sintering and grain growth procedure on heat rate, temperature and time to avoid the effect of the second eutectic at 1320 °C on the system, produces highly dense 5 mm size single crystals in a really easy experimental procedure. Presence of the phase BaTiSiO5 is important for the exaggerated grain growth by forming a liquid phase at 1260 °C (eutectic temperature between BaTiO3 and SiO2) during heat treatment. This phase moves through the bulk and defines four different zones of grain growth. A detailed description of the method and the grain growth mechanism are presented.