The phase diagram for the Bi2Te3&sngbnd;Sb2Te3pseudo‐binary system is of the solid‐solution type, where the distribution coefficientkis equal to unity at 33.3 and 66.7 mole % Sb2Te3. Theclat tice parameter remains essentially constant across the diagram at 30.49 Å for both slowly crystallized and quenched alloys. For quenched alloys thealattice parameter decreases almost linearly, from a value of 4.487 Å, for pure Bi2Te3, to a value of 4.275 Å, for pure Sb2Te3; however, a significant contraction from linear variation is found in slowly crystallized materials.EGdiminishes in an essentially linear fashion from 0.16 eV, for pure Bi2Te3, to 0.12 eV at 24.2 mole % Sb2Te3in both slowly crystallized and quenched materials.EGremains approximately constant from 24.2 to 66.7 mole % Sb2Te3for slowly crystallized materials but continues to drop for quenched materials.