Dielectric properties of Ag1-xAxNbO3(A: K, Na and Li) and AgNb1-xTaxO3solid solutions in the vicinity of diffuse phase transitions

Low-frequency (100 Hz-1 MHz) dielectric studies of the AgNb 1- x Ta x O 3 (ATN) (0⩽ x ⩽0.4), Ag 1- x K x NbO 3 (AKN) (0⩽ x ⩽0.04), Ag 1- x Li x NbO 3 (ALN) (0⩽ x ⩽0.04) and Ag 1- x Na x NbO 3 (ANN) (0⩽ x ⩽0.4) solid solution ceramics were carried out in the temperature range 120-700 K. The dielectric dispersion was only observed within the ferroelectric M 1 phase. For all the investigated materials the M 1 -M 2 phase transition exhibits the ferroelectric relaxor-like character. The relations between the frequency and the temperature ( T m ) of the maximum dielectric permittivity ε' only obey the Vogel-Fulcher law for the ALN ceramics. Measurements of remanent polarization P r were performed within the ferroelectric M 1 phase. Two different origins of the ferroelectric state are proposed. The possibility that the M 1 ferroelectric phase is of ferrielectric nature is also discussed. The diffuse M 2 -M 3 phase transition is frequency independent. These results allowed us to consider the coexistence of the ordered and disordered subsystems in silver niobate and its solid solutions.