Low-temperature pyroelectricity

The current state of the set of problems associated with the study and application of the pyroelectric effect at low (T<30 K) temperatures is outlined. The reasons for the qualitatively different temperature dependences of the total pyroelectric coefficient γ^σ(T) in linear pyroelectrics and ferroelectrics are discussed. An analysis is given of the reasons why the theoretical temperature dependences obtained for the primary pyroelectric coefficient γ^ε(T) adequately describe the experimental γ^σ(T) dependences for all materials studied. In this connection, the correctness of determining the secondary pyroelectric coefficient γ^S(T) from the macroscopically measured coefficients of thermal expansion is considered. The potential of thermodynamically nonequilibrium polar media and low-temperature pyroelectric materials is substantiated. The review consists of the following sections: (1) an introduction; (2) the theory of low-temperature pyroelectricity; (3) experimental procedures; (4) discussion of the experimental data: (A) perfect single crystals, (B) the problem of the secondary pyroelectric coefficient, (C) imperfect single crystals; (5) pyroelectric materials for low-temperature applications; and (6) a conclusion.