Effects of MgO-Doping on Electrical Properties and Microstructure of BaTiO₃

Abstract

Degradation behaviors of Mg-doped BaTiO3 have been studied in terms of oxygen vacancy concentration and microstructural development. Mg-doped BaTiO3 powders were precisely synthesized by the Pechini method. As MgO content was increased to 1.0 mol%, Curie points moved to lower temperatures and dielectric constants decreased. The specimens doped with MgO showed higher leakage currents under the continuously applied dc field at a high temperature (100°C) during the aging process, compared with the undoped BaTiO3. With low levels of MgO (<1.0 mol%), the microstructure is similar to that of undoped BaTiO3, whereas a significant reduction in grain size was observed with higher levels (>2.0 mol%).

Effects of Mn-doping on TSDC and degradation of BaTiO3

“…The maximum TSDC peak of Ba(Ti 0.99 Mn 0.01 )O 3−δ shifts to lower temperatures (<125 • C) compared with Ba(Ti 0.995 Mn 0.005 )O 3−δ , and the TSDC increases above the temperature (>125 • C) at which the maximum peak occurs. This result is compatible with the previous report that charged oxygen vacancies, in combination with acceptors, locally deform the perovskite unit cells, leading to the local reduction of the tetragonality and the decrease in the Curie temperature [13,43]. Fig.…”

“…(1). The equilibrium electrical conductivity indicated that oxygen vacancies are formed to compensate negatively charged Mg ions on Ti sites and the oxygen vacancy concentration of Ba(Ti 0.995 Mg 0.005 )O 2.995 is estimated to be ∼50 times greater than that of un-doped BaTiO 3 according to the relationship proposed by Smyth [13,42]. Such a large amount of oxygen vacancy formation leads to the severe electrical degradation as shown in Fig.…”

“…The increase in oxygen vacancy concentration by acceptor doping (Mn 3+ , Mg 2+ ) suppresses BaTiO 3 to be reduced as MLCC materials with Ni-electrodes. However, the oxygen vacancy is the most mobile ionic species in BaTiO 3 lattices and the electro-migration of charged oxygen vacancies in dc fields is accountable for the electrical degradation of BaTiO 3 -based ceramic capacitors [2,6,7,[11][12][13][14].…”

“…Defect chemistry and electrical properties of Mn-doped BaTiO 3 have been extensively studied by numerous researchers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The valence state of Mn ion is known to change from Mn 2+ to Mn 3+ or Mn 4+ with increasing oxygen activities, while Mg ion is constant by divalent [2,3,[6][7][8][9][10]16].…”

Effects of MgO coating on microstructure and dielectric properties of BaTiO3

“…This is similar to the previous study of MgO doped BaTiO 3 . 25 Excess MgO is assumed to exist in the grain boundary region and suppresses the grain growth, resulting in poor densification. Fig.…”