On the Bridgman growth of lead-tin selenide crystals with uniform tin distribution

The application of T-x-y phase diagram for the control of the crystal composition of alloy crystals during Bridgman growth is illustrated using (Pb1−xSnx)1−δSe1+δ solid solutions as an example. Within the framework of the proposed approach, the axial segregation can be minimised if the feed composition is chosen in the regions of phase diagram where the iso-mole-fraction lines are perpendicular to isotherms. For the system Pb-Sn-Se the component distribution in crystals grown from a melt with δ=0, a Se-rich melt (δ>0) and a metal-rich melt (δ<0) are discussed. Uniform crystals with x=(0.03-0.15)±0.01 can be obtained from Se-rich melt (Se enrichment is 12-5 at%Se, T=1280-1200 K). The use of metal-rich melt allows obtaining crystals with moderate segregation of 3-5 mol% SnSe for x=0.13-0.23 at 3-9 at% of metal enrichment and T=1270-1200 K and for x=0.35-0.45 at 25-35 at% of metal enrichment and T=1120-1050 K.