Dielectric Dispersion in Ferroelectric Ca2Sr(C2H5CO2)6

The complex dielectric constant ε (ω) of Ca 2 Sr(C 2 H 5 CO 2 ) 6 along the tetragonal c -axis was measured at 54 different frequencies between 10 3 Hz and 10 9 Hz. In the paraelectric phase, ε (ω) is well described by the Debye dispersion formula with a single relaxation time except in the vicinity of the Curie temperature T c . In the temperature region of \(0{<}T-Tc{}3\) K, the second dispersion of a resonant type is observed in addition to the Debye type dispersion. The temperature dependence of the relaxation time τ of the Debye dispersion is well expressed in the temperature rarnge \(1 K{}T-Tc\) by a power law, τ∝( T - T c ) - Δ with Δ =1.31, which is larger than the critical exponent γ=1.28 for the static dielectric constant obtained by extrapolation of the Debye dispersion.