The relationship between chemical composition distributions and specific grain boundary conductivity in Y-doped BaZrO3 proton conductors

Yang

et al. 2015

J. Ceram. Soc. Japan

We studied 3 BaZrO 3 (210)[001] tilt grain boundaries using density functional theory and a space charge layer model. Formation enthalpies of BaZrO 3 and competing oxides were calculated using fitted elemental-phase reference energy (FERE) correction, and a stable region of BaZrO 3 , as functions of Ba and O chemical potentials, was determined. Grain boundary energies were evaluated as functions of Ba and O chemical potentials within the determined stable region of BaZrO 3 from the FERE correction. Among the six tested grain boundaries, an energetically favorable nonstoichiometric grain boundary was determined. Based on the nonstoichiometric grain boundary, we calculated the electrostatic potential and concentrations of proton and oxygen vacancy using a space charge layer model.

Section: Bulkmentioning

confidence: 99%

Study of Σ3 BaZrO3 (210)[001] tilt grain boundaries using density functional theory and a space charge layer model

Yang

et al. 2015

J. Ceram. Soc. Japan

“…However, sintered BaZrO 3 is polycrystalline and the conductivity of that material is orders of magnitude lower due to resistance at the grain boundaries (GBs) [1,3,4]. Grain boundaries in BaZrO 3 do not contain secondary phases [5][6][7][8] and the high resistance is therefore considered to be an intrinsic effect.…”

Section: Introductionmentioning

confidence: 99%

Theoretical modeling of defect segregation and space-charge formation in the BaZrO3 (210)[001] tilt grain boundary

2013

Density-functional theory (DFT) has been used to determine the structure and interface energy of different rigid body translations (RBTs) of the (210)[001] grain boundary (GB) in BaZrO 3 . There exist several different stable structures with almost equally low interfacial energy. Segregation energies of protons and oxygen vacancies have been determined for the most stable (210)[001] grain boundary structure. The results suggest that both defect species favor segregation to the same site at the boundary interface with minimum segregation energies of −1.45 eV and −1.32 eV for vacancies and protons respectively. The segregation energies have been used in a thermodynamic space-charge model to obtain equilibrium defect concentrations and space-charge potentials at a 10 % dopant concentration. Space-charge potential barriers around 0.65 V were obtained at intermediate temperatures under hydrated conditions, where protons are the main contributor to the excess core charge. The potential is slightly lower under dry conditions.

“…On the contrary, high density ceramics can be sintered from sand milled powders at 1640°C for 15 h. Most notably, the sintered compact from the powders that were sand-milled for 5 h achieve almost their full density (99%), which is slightly higher than that prepared by Pechini method (almost 98% sintered at 1800°C for 20 h). 21), 22) These results indicate that sand milling at high rotation speed can efficiently eliminate the aggregation of calcined powders and greatly improve the sintering activity of powders.…”

Section: Resultsmentioning

confidence: 86%

Preparation and proton conductivity of ultrafine Y-doped BaZrO3 ceramics

Xia

Nian

et al. 2017

J. Ceram. Soc. Japan

Y-doped BaZrO 3 powders prepared by high-temperature solid state reactions often suffer the disadvantage of serious aggregation. In order to eliminate this disadvantage, planet-mill and sand-mill processing methods were employed. The results of particle-size determination and scanning electron microscopy images confirm that sand milling can efficiently eliminate the aggregation and produce ultrafine and well-dispersed Y-doped BaZrO 3 powders. Starting from powders treated by sand milling, completely densified Y-doped BaZrO 3 ceramics can be fabricated by sintering at a low temperature of 1640°C for 15 h. Y-doped BaZrO 3 ceramics sintered from powders treated by sand-mill for 5 h possess an ultrafine crystal size and a higher density and proton conductivity compared to those treated for 2 h.