Dielectric behavior of lead iron tantalate - lead titanate ceramics

Abstract

\nDielectric properties of complex perovskite Pb(Fe$_{1/2}$Ta$_{1/2})$O$_{3}$ (PFT) and its solid solutions with normal \nferroelectric PbTiO$_{3}$ (PT) were studied. The addition of 5 - 25 mol % \nof PbTiO$_{3}$ was used to shift upwards the temperature of the \nferroelectric-paraelectric transition of pure PFT. Dielectric permittivity \nand dissipation factor of the ceramics were determined in the temperature \nrange from –55 to 550 $^{\\circ}$C at frequencies 10 Hz - 1 MHz. Dc resistivities \nof the samples were measured in the temperature range 20 - 500 $^{\\circ}$C. The \nPFT-based ceramics sintered at 1050 $^{\\circ}$C showed a relatively high \ndielectric permittivity (3000 - 5700 at Curie temperature) and a high \nresistivity (10$^{11}$ - 10$^{13}\\,\\Omega$cm at 20 $^{\\circ}$C). Two broad \nmaxima in the dielectric permittivity versus temperature plots were observed \nat a given frequency. The location of the first one, corresponding to the \nferroelectric - paraelectric transition, changed from –30 $^{\\circ}$C for pure \nPFT to 80 $^{\\circ}$C for 0.75PFT-0.25PT ceramics. The second maximum, related to \ndielectric relaxation, occurred at higher temperatures in the range 200 - \n500 $^{\\circ}$C and was strongly dependent on frequency and the content of \ndopants.\n