Adiabatic elastic constants of uranium monocarbide

Using the phase-comparison technique, the room temperature adiabatic elastic constants of UC single crystals grown by the radio-frequency, induction heated floating-zone technique have been measured as a function of carbon composition (4.52–4.96 wt% C). The temperature dependence of the moduli was measured from 80 to 900 °K in a hypostoichiometric sample. There is a systematic increase of c₄₄ with increasing carbon concentration. The elastic-moduli values are compared with published values for some alkali halides and refractory metal monocarbides. An increase in temperature results in a linear decrease in c₁₁ and c, but c₄₄ increases with temperature to a maximum at 80°C. The temperature coefficients of the moduli at T ? 80 °C are comparable to those observed in the alkali halides. These results indicate that the ionic crystal character of the interatomic bonds increases with temperature and that the carbon concentration in the UC phase can deviate from stoichiometric composition.