Hydrothermal crystallization device with alternating temperature field and method for growing crystals by using device

The invention discloses a hydrothermal crystallization device with an alternating temperature field and a method for growing crystals by using the device. The hydrothermal crystallization device comprises a hydrothermal high-pressure kettle; the hydrothermal high-pressure kettle comprises a kettle body; the inner cavity of the kettle body is divided into three parts which sequentially comprise a first raw material dissolving area, a constant-temperature growing area and a second raw material dissolving area from bottom to top; when the hydrothermal high-pressure kettle is placed into a three-section type resistance furnace for heating, the temperature of each area in the inner cavity of the kettle body is controlled by the three-section type resistance furnace, wherein the temperature of the first raw material dissolving area has a certain temperature difference with the temperature of the second raw material dissolving area, and the temperature of the constant-temperature growing areais between the temperatu