With an aim to understand the origin of the low thermal expansion coefficients (TECs), cation substituted YBaCo4O7-type oxides have been investigated by in-situ neutron diffraction, bond valence sum (BVS), thermogravimetric analysis, and dilatometry. The compositions YBaCo3ZnO7+delta, Y(0.9)ln(0.1)BaCo(3)ZnO(7+delta), and Y(0.9)ln(0.1)BaCo(3)Zn(0.6)Fe(0.4)O(7+delta) were synthesized by solid-state reaction at 1200 degrees C. Rietveld refinement of the joint synchrotron X-ray and neutron diffraction data shows that the Zn and Fe dopants have different preferences to substitute the Co ions in the 6c and 2a sites. The bulk thermal-expansion coefficients of YBaCo3ZnO7+delta, Y(0.9)ln(0.1)BaCo(3)ZnO(7+delta), and Y(0.9)ln(0.1)BaCo(3)Zn(0.6)Fe(0.4)O(7+delta) are, respectively, 9.42, 9.76, and 9.06 x 10(-6) degrees C-1. Neutron diffraction data show that the low anisotropic TEC along the a-axis is the main contributor to the low bulk TECs. With the substitution of In, Zn, and Fe in Y(0.9)ln(0.1)BaCo(3)Zn(0.6)Fe(0.4)O(7+delta), the anisotropic and bulk TECs could be reduced to 8.94 and 9.06 x 10(-6) degrees C-1, respectively, mainly due to the suppression of the change in Co-O bond length in CoO4 polyhedra. The observed weight loss during heating is due to the loss of interstitial oxide ions, as revealed by neutron diffraction and BVS map. Y(0.9)ln(0.1)BaCo(3)Zn(0.6)Fe(0.4)O(7+delta) has the lowest area-specific cathodic polarization resistance of 0.14 Omega cm(2) (R-total/2) at 700 degrees C in air. (C) 2016 Elsevier B.V. All rights reserved.