Über den α-NaFeO2-Typ: Zur Kenntnis von NaCrO2 und KCrO2

on the α-NaFeO₂ type: about NaCrO₂ and KCrO₂ Single crystals of NaCrO₂ (“chromic-green”) and KCrO₂ (deep dark green), always hexagonal plates, were prepared for the first time. Homogeneous mixtures of Na₂O resp. K₂O (Na:Cr = 1.1 : 1 resp. K : Cr = 1.1 : 1) and Cr₂O₃ were heated in closed Ni-tubes at 1000°C (1100°C). Heating up and cooling down slowly. Corresponding powder samples were obtained at 500°C (700°C). Four-circle-diffractometer dates were used to derive the structure determining parameter z_o. Madelung part of lattice energy, MAPLE, was calculated.