Domain effects in the ferroelectric 'tungsten-bronze' KSr2Nb5O15

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Abstract
Differences in the polar dielectric constant and loss of the 'tungsten-bronze', KSr2Nb5O15 have been observed between the poled and unpoled states. Dielectric dispersion occurs in the multi-domain state at frequencies four orders of magnitude lower than in BaTiO3 crystals. An explanation of this behaviour is presented in which unsaturated material in the 180 degrees domain walls makes a large contribution to the dielectric constant and loss. Analogy is made between the behaviour of domain-wall material and the dielectric softening of bulk material at the ferroelectric-paraelectric phase transition.