Influence of nonstoichiometry on ferroelectric phase transition in BaTiO3

Abstract

The ferroelectric phase transition behavior in equilibrated nonstoichiometric BaTiO3 powder samples was characterized by a differential scanning calorimeter. The transition temperature (TC) and enthalpy of transition (ΔHTC) between the paraelectric and ferroelectric phases were varied systematically with defect concentrations through the Ba∕Ti ratio, temperature, and oxygen partial pressure [p(O2)]. It was observed that the different defects such as titanium, barium, and oxygen vacancies all contribute to the changes of TC and ΔHTC. The TC decreased with increasing concentration of TiO2 partial Schottky defects and BaO partial Schottky defects. The annealing temperature increased the TC due to a complex mechanism with the increase of full Schottky defect reactions. In terms of p(O2), TC is constant in the ionic compensation region, and increases with the nonstoichiometry in the electronically compensated p(O2) region.

Structural changes in potassium sodium niobate ceramics sintered in different atmospheres

“…The tetragonal-cubic peak in the sample sintered in N 2 has a smaller secondary peak next to it. This indicates that the sample may not have reached its equilibrium vacancy concentration during sintering [13]. The peaks of the sample sintered in 75N 2 -25H 2 (mol%) are broader and shallower and the orthorhombic-tetragonal peak at ∼90-100 • C is difficult to distinguish from the background.…”

“…Previous work on BaTiO 3 has found that varying the oxygen partial pressure of the sintering atmosphere can change the tetragonal-cubic transition temperature [12,13]. It can therefore be expected that changes in the sintering atmosphere will also change the structure of (K 0.5 Na 0.5 )NbO 3 .…”

Ferroelectric-thermoelectricity and Mott transition of ferroelectric oxides with high electronic conductivity

“…A comprehensive understanding of the solid solution and phase equilibria of BaTiO 3 was established. [138][139][140][141][142] As shown in those papers, the phase transition temperature decreased with an increased concentration of partial Schottky defects in nonstoichiometric Ba 1−x Ti 1−y O 3−(x+2y) . The defect concentration dependences of the phase transition temperature for BaO partial Schottky (BaTi 1−δ O 3−2δ ) and TiO 2 partial Schottky (Ba 1−δ TiO 3−δ ) defects are dT C /dδ = −2.2 ± 0.3 • C/δ and −8.2 ± 1.6 • C/δ, respectively, where δ has an increment of 0.01.…”

Effect of sintering condition and V-doping on the piezoelectric properties of BaTiO₃–Bi(Mg_1/2Ti_1/2)O₃–BiFeO₃ ceramics

“…A possible reason for this is the reduced oxygen vacancy concentration, as reported for BaTiO 3 . 35) At temperatures between room temperature and 200°C, a frequency dispersion in the dielectric constant and loss was observed for the V-doped sample and the embedded sample. A similar dispersion was found in BTBF and BTBiScO 3 solid solutions, 36), 37) and therefore this could be a characteristic of BaTiO 3 Bi-based perovskite systems.…”