Mass-difference impurity scattering

Furthermore, this critical concentration is quite low because discontinuities have been observed for concentrations of SDS as low as 100 wppm. This can explain, in part, the possible scatter in the experimental data. Also, the phenomena may not always be observed. Impurities by themselves do not explain the discontinuity. The level of elasticity in the fluid plays an important role in the appearance and the magnitude of the velocity jump. Table 3 lists the values of the magnitude of the velocity jump for different concentrations of polyacrylamide AP-273 in a 50 mass % aqueous glycerol... 

The effects of impurities and solid solutions on phonon conductivity in single-phase crystalline ceramics are discussed next. Impurities and solute atoms tend to decrease thermal conductivity. These increase the phonon scattering by way of differences in mass, binding force, and elastic strain field. As the temperature is raised, the scattering increases at low temperatures. At temperatures greater than about half the Debye temperature, it becomes independent of temperature. This is because the average wavelength at these temperatures becomes comparable with or less than the point imperfection. 

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