Growth of Sapphire Disks from the Melt by a Gradient Furnace Technique

Crystal growth by the heat exchanger method, spectroscopic characterization and laser operation of high-purity Yb:Lu2O3

“…Larger crystal boules of 25 cm 3 volume with single crystalline regions of 1 cm 3 dimensions could be grown by the Bridgman technique [19,20]. In order to reduce the strain and parasitic crystallization from the bottom and wall of the crucible, the heat exchanger method (HEM) was further used, which was demonstrated to be a suitable technique for the production of large-scale crystals [21]. With this technique it was possible to grow boules with monocrystalline regions of several cm 3 in the past [7].…”

Sapphire Crystal Growth and Applications

“…HEM is based on directed crystallization by cooling the melt under the conditions of a specific temperature gradient [28]. The crystal is grown in a molybdenum crucible the bottom of which is cooled by blowing gas (Fig.…”

“…Here is a progress report in the crystal dimensions grown by HEM: Crystals in the form of discs up to 70 mm in diameter and to 20 mm thick were grown in the first experiments [28,29]. Crystals up to 200 mm diameter were produced by 1975 [30] and up to 340 mm diameter have been available for production since 1996.…”

Vertical Bridgman growth of sapphire—Seed crystal shapes and seeding characteristics

“…This was so because the present VB method provides no mechanism to prevent the melting of the seed crystal, such as the He-gas cooling in the HE method [3,4].…”

“…Reproducible seeding with single-crystal growth was very difficult when we could observe neither the seed crystal nor the growth interface during the seeding process in either the HE or the VB method. In the HE method, a seed crystal placed at the bottom of the crucible is kept from melting by a cooling flow of He [3]. This allows seeding that reproducibly yields single-crystal growth, with the seed crystal remaining unmelted.…”