[en] The thermal expansion behavior of pure, Ge-doped and Li-doped hexagonal cordierites with respective compositions: 2Mg0 2Al₂O₃ 5SiO₂, 2Mg0 2Al₂O₃ 4SiO₂ GeO₂, and 2Mg0 (2+x)Al₂O₃ (5-2x)SiO₂ xLi₂O with x = .174, was investigated using time-of-flight neutron powder diffraction at temperatures from 22 to 750⁰C in vacuum. The data were refined in space group P6/mcc using the Rietveld method. The lattice thermal expansion curves of all 3 samples were quite similar. The negative c axis expansion is asociated with (1) displacement of the T₂ cations generally toward the c axis channels and (2) changes in the distortion of the coupled T₁/M tetrahedra/octahedra in the structure. Both contributions were present in all 3 samples but the first was more dominant in the Ge doped sample. The nature and origin of the distortions in T₁ and M are discussed