Zone refining is based on the principle of that the impurities tend to be in the melt than in the solid metal.
True
Metals like silicon Gallium and Germanium which are already very pure are subjected to Zone Refining or Fractional crystallization. This process reduces the impurity to ppm level;it is based on the principle that the impurities tend to stay in the melt. On solidification, pure metal solidifies just ahead of the surface of the melt.