Product Overview: The horizontal directional solidification method is used to synthesize polycrystals. The directional solidification furnace consists of three temperature zones. Taking gallium arsenide (GaAs) polycrystals as an example, arsenic sublimates in the low-temperature zone (around 630°C), passes through the intermediate-temperature zone, and gradually reacts with gallium in the high-temperature zone (1250–1255°C) to form GaAs polycrystals. PBN boats are used as reaction vessels in the high-temperature zone.