Influence of Grain Size on Impedance Spectra and Resistance Degradation Behavior in Acceptor (Mg)‐Doped BaTiO₃Ceramics

Abstract

The effect of acceptor concentration in (Mg)‐doped BaTiO3 on the resistance degradation behavior was contrasted between coarse‐ and fine‐grain samples with ∼90 and ∼0.8 μm in size, respectively. Both cases showed similar trends that the time to degradation decreased systematically with the increase of acceptor concentration, however the absolute rates are very different for a given dopant concentration. Although the grain size and grain boundaries are important, it is also shown through an impedance analysis that the degradation behavior depends on the grain conductivity (σg) and ionic transference number (tion) as evaluated by the Warburg impedance. Under the condition of the same nominal acceptor concentration, fine‐grain samples showed much lower grain conductivity (σg) but little differences in the grain boundary conductivity (σgb) than that of coarse‐grain samples. The ionic transference number (tion) was also much smaller in fine‐grain samples. These results show that the actual effective acceptor concentration on being ionically compensated to enhance oxygen vacancies becomes smaller with the decrease of grain size. This fact coupled to the increase of the number of grain boundaries accounts for the improved degradation behavior with the decrease of grain size.

Field-enhanced bulk conductivity and resistive-switching in Ca-doped BiFeO3 ceramics

“…Thus, it does not require oxide ion (or vacancy) transport, although this is suggested to be a key requirement in other memristive studies [23][24][25][26][27][28][29][30][31]. It does not require electron injection at the cathode, although evidence for this has been obtained from electrocolouration effects in other materials [23][24][25][26][27][28][29][30][31]. It does not require a cation-based mechanism for hole creation at The results reported here on Ca-doped BiFeO3 are different in nature but not in mechanism from that seen with various acceptor-doped titanate perovskites [17][18][19][20][21][22].…”

Role of polaron hopping in leakage current behavior of a SrTiO3 single crystal

“…By numerically solving the coupled equations (Eqs. (3), (5), (7), and (8)) with appropriate boundary conditions (Eqs. (6), (9), (10), and (19)), we obtained the equilibrium profiles of space charges and interior electric potential for the initial unbiased condition as shown in Fig.…”

“…6 Yoon et al suggested that the increase of effective acceptor concentration (Mg) of BaTiO 3 as the grain size decreases causes high oxygen vacancy concentrations, leading to faster degradation rates. 7 Yoon also found out that the space charge polarization at grain boundaries by the charge carriers of pre-dominant holes and small portion of oxygen vacancies results in dielectric relaxation in BaTiO 3 . 8 Despite all these works, however, due to the complexity that many factors may influence the degradation, such as acceptor doping, polarization current, dielectric layer thickness, and electrode microstructure, the key mechanism of resistance degradation has not yet been well understood experimentally.…”

Voltage‐Dependent Bulk Resistivity of SrTiO3:Mg Ceramics

“…To understand these results, we consider first a widely accepted explanation for dc bias effects, primarily due to Waser et al . Dielectric ceramics containing oxygen vacancies, , incorporated by acceptor doping, show a slow increase in leakage current under dc field stress and with increasing temperature.…”