Synthesis of High-Quality Forsterite

To establish a process that produces high-quality forsterite stably, calcining and sintering conditions were investigated chiefly and two kinds of silica with different forms, and grain sizes were used as starting raw materials. On the basis of the quality factor (Qf) for forsterite, the sintered samples prepared using powders calcined for 10–24 h, were found to be more stable than those in the case of 2–4 h, and in the case of 24 h of calcination, the samples showed a single phase of forsterite with fine grains. Silica with an amorphous form and a small grain size of 0.25 µm brought a higher Qf value and a wider permissible temperature range of sintering than silica with a crystalline form and a coarse grain size of 0.82 µm. Concerning the sintering temperature, the sample sintered above 1400 °C showed a high Qf value. The Qf value of the sample calcined at 1175 °C for 24 h and sintered at 1450 °C for 2 h using fine-grain amorphous silica of 0.25 µm size, was improved to 219,200 GHz.