Vertical Bridgman growth of sapphire crystals, with thin-neck formation process

•A new technique is proposed in the traditional vertical Bridgman growth of sapphire crystals, in which thin-neck formation follows the initial seeding.•Low-angle grain boundaries generated at the periphery of the seeding interface were eliminated at the thin neck.•The c-axis sapphire crystals with main bodies free from low-angle grain boundaries were grown.

A new technique is proposed in the traditional vertical Bridgman growth of sapphire crystals, in which thin-neck formation follows the initial seeding. Low-angle grain boundaries generated at the periphery of the seeding interface were eliminated at the thin neck, and the c-axis sapphire crystals with main bodies free from low-angle grain boundaries were grown.