Charge transfer in liquid semiconductors: The K-Te system

The neutron diffraction patterns of molten ${\mathrm{K}}_{\mathit{x}}$ ${\mathrm{Te}}_{1\mathrm{-}\mathit{x}}$ alloys for x=0.12 and x-0.50 demonstrate the persistence of covalently bonded tellurium in the liquid. In the case of liquid ${\mathrm{K}}_{0.12}$ ${\mathrm{Te}}_{0.88}$, the measured structure is domianted by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium. The equiatomic alloy ${\mathrm{K}}_{0.50}$ ${\mathrm{Te}}_{0.50}$ is shown to contain mostly Te pairs which are identified with Zintl ions, ${\mathrm{Te}}_2^{2\mathrm{-}}$. The presence of these ions explains the semiconducting behavior of these alloys deduced from recent electrical transport measurements.