Influence of heat distribution and zone shape in the floating zone growth of selected oxide compounds

The effects of heat distribution, process parameters, and the ambient atmosphere on the characteristics of the molten zone are considered for floating zone (FZ) crystal growth of selected oxide compounds with special reference to cuprates. The outer shape of the FZ, which is stabilized only by capillary forces, and the interfaces between melt and growing crystal are decisive for process stability and crystal perfection. They do not only depend on external parameters such as zone heights, growth velocity, and rotation mode but are closely related to the phase diagram and the constitution of the individual substance. Therefore, the choice of the optimum process conditions is a subtle balance of parameters like appropriate focusing or defocusing of the light, the direction of growth and the ambient atmosphere, which are adapted to the individual substance. A pyrometric method of FZ temperature measurement was developed as an appropriate tool for process control.