We report here the synthesis and infrared characteristics of the solid solution of the layered oxycarbonates Sr2-xBaxCuO2(CO3) (0 ≤ x ≤ 2). Synthesis, under partially enclosed conditions, from (Sr, Ba)CO3 and CuO is observed to give enhanced stability of the oxycarbonate as the partial pressure of CO2 over the sample appears to retard both the reaction and the subsequent decomposition of the oxycarbonates. Compounds with higher barium content are more stable, in keeping with the considerable stability of BaCO3 with respect to decomposition. The a lattice constant shows an anomalously large increase at high barium content, accompanied by an anomaly in the Cu-O inplane vibration occurring at around 500 cm-1 and an accompanying loss of antiferromagnetic order. Both effects are attributed to the presence of additional oxygen in the structure of compounds at these stoichiometries, analogous to that found earlier for (Ba, Sr)2CuO3+δ materials. © 1993 Academic Press, Inc.
