Optical properties of PbTe and PbSnTe doped with Cr

Single crystal samples of PbTe and PbSnTe doped with Cr were made using the Bridgman technique. Far infrared diagrams of PbTe samples doped with 0.4 at.%, 0.8 at.% and 1 at.% Cr and also of Pb(0.9)Sn(0.1)Te doped with 0.4 at.%, 0.7 at.% and 1.1 at.% Cr are presented and numerically analyzed. Local modes were determined at about 260 cm(-1) and 480 cm(-1) for PbTe doped with Cr and at slightly higher frequencies for PbSnTe doped with Cr. The origin of the local modes was discused about the possible application of the PbSnTe + Cr alloys