The phase equilibria in the 1/2Nd(2)O(3)-BaO-1/2Fe(2)O(3) system were systematically studied at 1373 K in air and presented in the form of a phase diagram. By X-ray diffraction (XRD) analysis of quenched samples, the homogeneity ranges and crystal structure were determined for the following intermediate oxides: Nd1-xBaxFeO3-delta with 0.0 <= x <= 0.05 (space group (SG) Pnma) and with 0.6 <= x <= 0.7 (SG Pm-3m), Ba6+yNd2-yFe4O15-delta with 0.0 <= y <= 0.4 (SG P6(3)mc), and Ba1.1Nd1.9Fe2O7-delta (SG P4(2)/mnm). The structural parameters of single-phase oxides were refined by the Rietveld method. The changes in oxygen content for Nd1-xBaxFeO3-delta (0.6 <= x <= 0.7), Ba6Nd2Fe4O15-delta, and Ba1.1Nd1.9Fe2O7-delta versus temperature in air were determined by thermogravimetric analysis. Gradual substitution of neodymium by barium in the Nd1-xBaxFeO3-delta (0.6 <= x <= 0.7) oxides leads to a decrease of oxygen content. Partial ordering via formation of separate domains with a(p) x a(p) x 5a(p) superstructure in Nd0.4Ba0.6FeO3-delta, which cannot be detected by XRD, noticeably influence its thermal expansion and electrical conductivity.