The true thermal expansion of uranium mononitride

The thermal expansion of uranium mononitride (UN) is calculated using in situ neutron powder diffraction data between 673 – 1273 K. The true, or instantaneous, thermal expansion describes the instantaneous rate of dimensional change at a given temperature. The true thermal expansion coefficient of UN calculated from this work and all available literature values are within error. The true linear thermal expansion coefficient ( α t ) of UN between 250 K and 2523 K is described by: α t = 6.5 ( 2 ) × 10 − 6 + 3.0 ( 2 ) × 10 − 9 T This can be converted to the mean linear thermal expansion coefficient ( α m ), for any T 0 and T value in the temperature range, using the equation: α m = exp [ 6.5 × 10 − 6 ( T − T 0 ) + 3.0 × 10 − 9 2 ( T 2 − T 0 2 ) ] − 1 T − T 0