Abstract The thermal behaviour of [Ba(HOC2H4OH)2Ge(OC2H4O)3] (2) as a BaGeO3 precursor, and its phase evolution during thermal decomposition in different atmospheres are described herein. The precursor complex decomposes in air to a finely divided mixture of BaCO3 and GeO2, which subsequently reacts above 650 °C to orthorhombic BaGeO3, transforming above 800 °C to hexagonal BaGeO3. The shrinkage behaviour of BaGeO3 compacts made from the as-prepared powders as well as from conventional mixed-oxide powders has been investigated. The samples were characterised by Fourier transformed infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), dilatometric measurements and thermoanalytic investigations (TG/DTA).