We present transmission electron microscopy results on ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te alloys that show evidence for a compositional instability for x≊0.5 when the alloys are grown on ${\mathrm{BaF}}_2$ substrates. The ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te alloy becomes stable at room temperature if a buffer layer of PbTe is grown on the ${\mathrm{BaF}}_2$ substrate prior to the growth of the ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te layer. The stabilization of the ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te solid solution is the result of the additional energy term due to the strain between the ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te film and the PbTe buffer layer. The estimated critical temperatures for decomposition of the ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Eu}}_{\mathrm{x}}$Te alloys with and without the PbTe buffer layer are ≊0 and ≊366 K, respectively, in accord with the experimental observations.

• Received 28 December 1988

DOI:https://doi.org/10.1103/PhysRevB.39.10995