We study the nonlinear absorption of high-power 10 µm radiation propagating through n-Ge, GaAs, and ZnSe materials widely used in the long-wave infrared range. Measurements are performed using both nanosecond and picosecond CO2 laser pulses providing intensities up to 100MW/cm2 and 5GW/cm2, respectively. Nonlinear absorption coefficients in optical quality n-Ge are found to be the same for both pulse durations. The nonlinear absorption coefficient of these materials scales inverse proportionally to their bandgap energies, indicating increased photoionization in the smaller bandgap materials.