Comment on 'Relaxor behavior and dielectric relaxation in Pb(Ba_1/3Nb_2/3)O_3: A phase pure new relaxor material' [J. Appl. Phys. 109,014114 (2011)]

摘要

Baipaj et al} have synthesized and investigated dielectric properties of Pb(Ba_1/3Nb_2/3)O_3 (PBN) ceramics. In this comment, we emphasize that the dielectric data analysis in Ref. 1 is not reasonable. Baipaj et al} perform a Curie-Weiss fit of reciprocal dielectric permittivity at 1 kHz for PBN (Fig. 4 in Ref. 1). However, at this frequency dielectric losses for PBN are very high (tgδ 1) in the whole temperature range from 275 to 425 K (Fig. 3 inset in Ref. 1). Therefore, the dielectric permittivity at 1 kHz is not a static (frequency-independent) dielectric permittivity.2 For ferroelectrics, the Curie-Weiss law is valid only for the static dielectric permittivity.3 The discrepancy between the Curie-Weiss fit and the reciprocal dielectric permittivity below 401 K is not a sign of the dielectric relaxation onset in PBN. In reality the dielectric relaxation at 1 kHz in PBN is observed already at substantially higher temperatures (Figs. 3, 7, and 8 in Ref. 1). Therefore, the conclusion of Baipaj et al} that 401 K is the Burns temperature for PBN is not reasonable. It was also demonstrated that finding the Burns temperature from the dielectric data is difficult.