Bismuth zinc niobate pyrochlore, a relaxor-like non-ferroelectric

Abstract

Fixed frequency plots of ε and tan δ versus temperature for (Bi 1.5Zn 0.5)(Zn 0.5Nb 1.5)O 7 (BZN) ceramics with the pyrochlore structure show relaxor-like response below ∼180 K with frequency-independent permittivity of ∼130 above ∼180 K and over the frequency range of 10 3-10 6 Hz. Impedance data in the range, 10-180 K fit an equivalent circuit derived from the classic dielectric relaxation circuit in which the relaxation resistance is replaced by a constant phase element (CPE). Temperature dependence of the circuit parameters shows that BZN is not ferroelectric; the CPE, which is responsible for the relaxor-like behavior, gradually changes from primarily capacitive to primarily resistive with increasing temperature.