The effect of uniaxial stress along [100] on the unstable A1 (TO) phonon, 47 cm-1 at room temperature, in ferroelectric (\u3c159°C) gadolinium molybdate has been studied by Raman scattering at 138, 141, 146, and 155°C. An increase in peak frequency and narrowing of the line shape is observed with increasing stress. The data are analyzed by fitting to a Lorentzian line shape. The force-constant parameter is insensitive to both stress and temperature, whereas the damping constant decreases nonlinearly with stress, approaching an asymptotic value at high stress
