The temperature dependent lattice parameter, c(T), was determined for samples of graphite, and HNO3 -graphite intercalates stage 3 and stage 4, using neutron diffraction. The temperature range studied is 12 to 300 K. The stage 3 and stage 4 intercalates exhibit a strong two-step discontinuity at the temperature of their structural phase transition (≈260 K). A stage-independent, temperature-dependent lattice parameter for the intercalant layer is extracted from the observed lattice parameters for graphite, stage 3, and stage 4 intercalates. The graphite and the intercalant lattice parameters are calculated using one-dimensional Debye theory in the framework of the Grüneisen relation. The Debye temperatures that yield best fits to the observed lattice parameters of the graphite and the intercalant are 500 K and 421 K, respectively. Using these values, thermal expansion coefficients for graphite, the intercalates and the intercalant are derived.