Probing disorder in cubic pyrochlore Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films

Abstract

The dielectric response of pulsed laser ablated Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films are investigated within the temperature range of 300-660 K and frequency range of 100 Hz-100 kHz. Thin film exhibited a strong dielectric relaxation behavior. A sharp rise in dielectric constant of BZN thin film at high temperatures is related to disorder in cation and anion lattices. Observed dielectric relaxation implies a redistribution of charges within the unit cell. This phenomenon suggests that the large change in dielectric constant is due to a dynamical rise of dipolar fluctuations in the unit cell. XPS spectra of BZN (A₂B₂O₆O') cubic pyrochlore, confirm that the relaxation corresponds to the ionic hopping among the A and O' positions of several local potential minima. Barrier height for hopping is distributed between 0 and 0.94 eV. The O 1s spectrum confirms presence of two types of oxygen in BZN thin film. The disorder in charge neutralized thin film is correlated with XPS spectra.