The changes in lattice parameter and oxygen non-stoichiometry in BaZr0.9Dy0.1O3-delta (BZDy10) were studied by high temperature X-ray diffraction (HT-XRD) and thermogravimetric analysis (TGA) as a function of temperature at three oxygen partial pressures. The experiments were performed under dry conditions to prevent the competition with the hydration reaction. The decrease of the lattice parameter with increasing oxygen partial pressure confirms the oxidation from Dy3+ to Dy4+ with the consumption of oxygen vacancies. The change in oxygen non-stoichiometry (Delta delta) measured by TGA showed similar trends: delta decreases with increasing oxygen partial pressure, in agreement with the oxidation of the dysprosium cations. The changes in Dy3+ concentration were estimated from the lattice strain, and in combination with the TGA data, were found to be consistent with a defect model where changes in oxygen non-stoichiometry are compensated fully by Dy valence changes rather than by oxygen-site polarons. Comparison of XRD and TGA data also enabled determination of isostoichiometric coefficients of thermal expansion (6.68-7.44.10(-6)/degrees C, below 450 degrees C, depending on gas atmosphere) and isothermal coefficients of chemical expansion (similar to 0.06) for dry BZDy10.