Short-term synthesis of poly- and single-crystalline iron monochalcogenides

Poly- and single-crystalline samples of the Fe(Se,Te)_{1 − δ} system have been synthesized for short times by annealing bulk iron in chalcogen vapors and by reacting powdered iron with chalcogen melts. The lattice unit cell parameters and critical temperatures (T _c) of the superconducting transition in the synthesized compounds agree with published data for the materials obtained by long-term synthesis using other methods. For Fe(Se_0.8Te_0.2)_0.82 block crystals, the temperature dependence of the second critical field in the vicinity of T _c is linear with a slope of −4.9 T/K.