The perfection of tungsten single crystals grown from the melt and solid state

High-temperature gradients at the solid-liquid interface during the growth of W single crystals from the melt by electron beam floating-zone melting d o not allow one to grow high-purity W single crystals free from small-angle boundaries with misorientation angles less than 3-5 min of are and subgrai n dislocation densities of less than 2 x 10(6) cm(-2). W single crystals wi th a more perfect crystallographic structure can be obtained by strain anne aling. In such single crystals there are no subboundaries and the dislocati on density is about 8 x 10(4) cm(-2). (C) 1999 Elsevier Science Ltd. All ri ghts reserved.