Electrical properties of sol-gel derived pyrochlore-type bismuth magnesium niobate Bi2(Mg1/3Nb2/3)2O7 thin films

A new type of Bi-based relaxor, Bi2(Mg1/3Nb2/3)2O7 (BMN), has been investigated to understand nature of relaxor behavior. The BMN thin films have been successfully fabricated by a sol-gel spin coating method on Pt/Ti/SiO2/Si(1 0 0) substrate. Dielectric properties of BMN thin films were investigated in the temperature range of 20-750 °C at frequencies of 102-107 Hz. The BMN thin film exhibits a characteristic diffused phase transition; the decreased dielectric constant and the increased dielectric constant maximum temperature with increasing frequency. The temperature dependent reciprocal dielectric constant (1/ε′) deviates from the Curie-Weiss law in the temperature range over the dielectric constant maximum temperature (Tm). The diffuseness of the phase transition of BMN thin film was estimated by calculating the difference between Tm and Tcw (starting temperature following the Curie-Weiss law). For BMN thin film, the Curie-Weiss temperature Θ, the Curie-Weiss constant c, the temperature Tcw and the temperature difference Tcw-Tm measured at frequency of 103 Hz are 912, 1.15×105, 969 and 49 K, respectively. The dielectric relaxation obeys the Vögel-Fulcher relationship with the freezing temperature of 770 K.