Ferroelectric materials with Bi-layered structure such as SrBi2Ta2O9 and Sr
Bi2Nb2O9 are now intensively investigated in view of their applications in
nonvolatile computer memories and high-temperature piezoelectric transducer
s. When Sr2+ is substituted with Ba2+, a significant disorder is induced an
d the material exhibits broadening of the phase transition. Such broadening
is essential for applications since it allows achieving smooth temperature
characteristics while maintaining high dielectric and piezoelectric proper
ties. In this work, stoichiometric dense BaBi2Nb2O9 (BBN) ceramics are sint
ered using a mixed oxide route. Dielectric and ferroelectric properties are
investigated in a broad range of temperatures and frequencies. Strong disp
ersion of the complex relative dielectric permittivity is observed includin
g typical relaxor features such as shift of the permittivity maximum with f
requency and broadening of the relaxation time spectrum with decreasing tem
perature. The dielectric relaxation obeys the Vogel-Fulcher relationship wi
th anomalously low freezing temperature (T(f)approximate to 100 K), which i
s much lower than the permittivity maximum in the radio-frequency range. Po
larization hysteresis loops testify linear properties of BBN at all tempera
tures above T-f. The properties of BBN ceramics are compared to conventiona
l relaxor systems such as Pb(Mg, Nb)O-3 and (Pb, La)(Zr, Ti)O-3. (C) 2001 A
merican Institute of Physics.