PREPARATION AND CRYSTALLOGRAPHIC PROPERTIES OF BACRO3 POLYTYPES

Several hexagonal BaCrO3 polytypes were prepared at high pressures and high temperatures in a tetrahedral anvil apparatus. Two systems were studied: (a) the reaction of CrO2 with BaO and (b) the reaction of CrO2 with Ba2CrO4. The reaction temperature and the reactants utilized were influencing factors in the formation of the various poly types. Single crystals of the 4-, 6-, 9-, 12-, 14-, and 27-layer modifications of hexagonal BaCrO3 were isolated in various experiments. The space groups of the polytypic phases were determined from single-crystal X-ray studies, and refined cell dimensions for most of the phases were obtained using Guinier X-ray powder diffraction data. Reactions at pressures less than 3000 atm did not yield BaCrO3. © 1969, American Chemical Society. All rights reserved.