  The controversy concerning the temperature correction to the Casimir force
has been ongoing for almost a decade with no view to a solution and has
recently been extended to include semiconducting materials. We review some
theoretical aspects of formal violations of Nernst's heat theorem in the
context of Casimir Lifshitz thermodynamics and the role of the exponent of the
leading term of the dielectric permittivity with respect to imaginary
frequency. A general formalism for calculating the temperature corrections to
free energy at low temperatures is developed for systems which do not exhibit
such anomalies, and the low temperature behaviour of the free energy in a gap
between half-spaces of poorly conducting materials modelled with a Drude type
permittivity is calculated.
