Impact of Defect Structure on ’Bulk’ and Nano-Scale Ferroelectrics

DFT computations combined with semiempirical modeling of variations with temperature of spectroscopic and magnetic properties of Gd3+-doped PbTiO3

“…It is worth noting that the reduction in T tr ≈ 700 K 49 observed in nanopowders was related to a size-driven phase transition associated with a critical mean particle size (16 nm). Raman spectroscopy measurements 48 revealed the structural changes that were ascribed to the cations of PbTiO 3 in phase II moving away from the center of the anion lattice, thus creating an inner electric field with spontaneous polarization and a permanent electric moment.…”

“…Some structural phase transitions have been observed in pure PbTiO 3 (PTO) with decreasing or increasing temperature. 47,48 For example, accurate measurements of lattice constants of PTO by Kobayashi et al 47 in the low temperature region have revealed a symmetry descent from tetragonal to orthorhombic or monoclinic phase at 183 K. Two phases in the high temperature region have been detected: a ferroelectric phase (phase II) and a paraelectric phase (phase I) below and above the Curie temperature T tr = 763 K, respectively. Knowledge of the mechanisms of ferroelectric-paraelectric phase transitions is important for in-depth understanding of the physical and electro-mechanical properties of ferroelectric materials.…”

Elucidating the capacitive behavior of Gd-doped BNT-BKT-BT electrodes in All-in-One supercapacitor devices

“…Gd was specifically selected here because Gd 3+ ions have strong paramagnetic fine and hyperfine EPR signals due to their electronic configuration. EPR spectroscopy of the Gd 3+ ion, with a 4f 7 electronic configuration ( 8 S 7/2 ), can be observed at room temperature [30]. Previously, EPR spectroscopy has been used to understand the site symmetry behavior of several different metal ion doped binary and trinary solid solution perovskitic systems such as "soft" (Gd, Fe)-codoped Pb(Zr 0.525 Ti 0.475 )O 3 [27], Fe 3+ doped (Bi 0.5 Na 0.5 )TiO 3 -BaTiO 3 -(K 0.5 Na 0.5 )NbO 3 [31], Cu 2+ doped 0.92(Bi 0.5 Na 0.5 )TiO 3 -0.06BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 [32], Mn 2+ doped (Bi 0.5 Na 0.5 )TiO 3 -BaTiO 3 [33], Mn 2+ doped (1-x)BiScO 3 -xPbTiO 3 (BSPT) [34], and recently Mn 2+ doped 0.65Pb(Mg 1/3 Nb 2/3 )O 3 -0.35PbTiO 3 (PMN-PT) piezoceramics [35].…”