Oxygen vacancy-related dielectric relaxation and electrical conductivity in La-doped Ba(Zr0.9Ti0.1)O3 ceramics

Abstract

Ba 1-x La x (Zr 0.9 Ti 0.1 ) 1-x/4 O 3 (BLZT) ceramics with x = 0.02 (BLZT-1), 0.04 (BLZT-2), 0.06 (BLZT-3) and 0.08 (BLZT-4) were prepared by a solid-state reaction route. Crystal structure of the BLZT ceramics was determined using X-ray diffraction and Raman spectroscopy. While the ceramics for x B 0.04 are pure phase with cubic perovskite structure, pyrochlore La 2 Zr 2 O 7 appears in the samples with x = 0.06 and 0.08. Dielectric properties as function of temperature and frequency showed more than one dielectric anomaly were found at high temperatures during heating but they weakened or disappeared during cooling. Both dielectric relaxation and electrical conductivity were taken into account in point defect mechanism. The double-ionized and short-range hopping of oxygen vacancy should be mainly responsible for the dielectric anomalies and conduction behavior. Activation energy of conductivity E con is lower than half of the band gap E g obtained by UV-Vis spectroscopy, which results from emergency of oxygen vacancies. In visible light region, the ceramics show a strong absorption with band gap of about 3.57 eV.

Metastable Bi2Zr2O7 with Pyrochlore-like Structure: Stabilization, Oxygen Ion Conductivity, and Catalytic Properties

“…The log σ dc (S cm –1 ) was plotted against 1000/ T (K –1 ) as per the Arrhenius relation given below: From the slope of conductivity versus 1/ T plot, activation energies ( E a ) at high and low temperatures were estimated to be 0.75(05) eV and 0.53(09) eV, respectively (Figure b). These values were within the range (0.3–1.2 eV) typically reported for processes involving oxygen vacancies. , As the conductivity activation energy ( E cond = 0.75 eV) at high temperature was nearly half of the direct band gap ( E g = 2.00 eV), conduction in this system should be due to thermally activated mechanism involving oxygen vacancies located near the Fermi level . The variation of dielectric loss (tan δ) with frequency at different temperatures was plotted in Figure c, in which distribution of conductivity from lower to higher frequency with increasing temperature of the sample was evident.…”

“…31,32 As the conductivity activation energy (E cond = 0.75 eV) at high temperature was nearly half of the direct band gap (E g = 2.00 eV), conduction in this system should be due to thermally activated mechanism involving oxygen vacancies located near the Fermi level. 33 The variation of dielectric loss (tan δ) with frequency at different temperatures was plotted in Figure 5c, in which distribution of conductivity from lower to higher frequency with increasing temperature of the sample was evident. With increasing temperature, conductivity of the sample increased, which could be attributed to higher mobility of ions at high temperature.…”

Interplay between Defects and Cation Nonstoichiometry in Lithium-Substituted CdGa2O4 Leading to Multifunctional Behavior

“…Activation energy in the ranges of 0.3–0.5 and 0.6–1.2 eV have been reported to be associated with singly and doubly ionized oxygen vacancies, respectively. ,− Therefore, the activation energy estimated in the current system might be due to doubly ionized oxygen vacancies. From the PL spectrum, where the oxygen vacancies caused emission, the band gap was estimated to be 2.35 eV, and half of it more or less matched the activation energy estimated . With this background, the following defect structure could be proposed.…”

“…From the PL spectrum, where the oxygen vacancies caused emission, the band gap was estimated to be 2.35 eV, and half of it more or less matched the activation energy estimated. 47 With this background, the following defect structure could be proposed. Substituting Cd 2+ with Li + at the tetrahedral site of the spinel structural arrangement would generate a singly ionized hole.…”

La2O3 modified 0.4(Ba0.8Ca0.2)TiO3–0.6Bi(Mg0.5Ti0.5)O3 ceramics for high-temperature capacitor applications

“…Rare earth element La often was employed to modify the dielectric properties of BaTiO 3 based compounds [11]. In this study, the high-temperature dielectric properties of the 0.4(Ba 0.8 Ca 0.2 ) (1-x) La 2x/3 TiO 3 -0.6Bi(Mg 0.5 Ti 0.5 )O 3 system with x=0, 0.15, 0.3 were investigated.…”