Design And Simulation Of The Furnace For The Growth Of Ferroelectric Single Crystal

Recently, the effort has been focused on the growth of large size and high quality ferroelectric crystals as the extensive application of these crystals in the domains such as medical ultrasonic transducers, underwater transducers and acoustic sensors. Growth methods of ferroelectric crystals mainly included the flux method, falling temperature method and Bridgman method. Although the Bridgman method was a well-suited technique for the growth ferroelectric crystals with large size and stable performance, the defect was still existence due to the component segregation and molten convection. In view of the above factors, the simulation of temperature field and effects of magnetic field on the growth equipment of ferroelectric crystals were very significant for the growth of high-quality ferroelectric crystals.In this paper, we designed firstly the structure of the growth furnace. Secondly, we simulated the temperature field of the furnace, including the transverse temperature field and the longitudinal temperature field. Thirdly, in order to introduce magnetic field, we designed a reasonable magnetic device, and the strength of magnetic field was simulated by the finite element. The results indicated that:A furnace with three-stage structure, including 300mm high-temperature segment with MoSi2 heating element,200mm medium-temperature segment and 300 mm low-temperature segment with resistance wire was designed. The height, diameter and thickness of insulting layer were 1082mm,402mm and 208mm, respectively. Based on the simulation of the transverse temperature field, a non-linear curve of temperature dependence on radii was obtained, and the temperature of furnace casing was suggested as 108.65℃. The temperature value was very important for the design of magnetic device and the choice of magnetic materials. Similarly, the longitudinal temperature field was also simulated under falling temperature conditions, and the temperature gradient curve in vertical was obtained. According to the simulated date, we proposed that when cooling the furnace with a constant speed, the time dependence of locations of isothermal surfaces with 1032℃ and 1265 ℃ were non-linear. The magnetic devices with iron hoop and without iron hoop were designed and simulated by Femm finite element analysis. For the magnetic devices without iron hoop, a uniform magnetic field with 420mT was suggested in the furnace center. However, the magnetic field in the furnace center, for the magnetic devices with iron hoop, was 160mT.