“…Meanwhile, the permittivity values of y = 1.0 increased again in the paraelectric temperature ranges. Such recurrent increases were often observed in Pb(Fe 1/2 Ta 1/2 )O 3 , 17,18 Pb(Fe 1/2 Nb 1/2 )O 3 , 19,20 and Pb(Fe 2/3 W 1/3 )O 3 , 9,17 which were explained by the interfacial polarization at the thin grain boundary layers 18,19,21 or by oxygen vacancies associated with the valence change in Fe. 22 Permittivity values of the entire compositions are shown in Fig.…”