Low‐Temperature Sintering of β‐Spodumene Ceramics Using Li2O–GeO2 as a Sintering Additive

Low‐temperature sintering of β‐spodumene ceramics with low coefficient of thermal expansion (CTE) was attained using Li₂O–GeO₂ sintering additive. Single‐phase β‐spodumene ceramics could be synthesized by heat treatment at 1000°C using highly pure and fine amorphous silica, α‐alumina, and lithium carbonate powders mixture via the solid‐state reaction route. The mixture was calcined at 950°C, finely pulverized, compacted, and finally sintered with or without the sintering additive at 800°C–1400°C for 2 h. The relative density reached 98% for the sample sintered with 3 mass% Li₂O–GeO₂ additive at 1000°C. Its Young's modulus was 167 GPa and flexural strength was 115 MPa. Its CTE (from R.T. to 800°C) was 0.7 × 10^?6 K^?1 and dielectric constant was 6.8 with loss tangent of 0.9% at 5 MHz. These properties were excellent or comparative compared with those previously reported for the samples sintered at around 1300°C–1400°C via melt‐quenching routes. As a result, β‐spodumene ceramics with single phase and sufficient properties were obtained at about 300°C lower sintering temperature by adding Li₂O–GeO₂ sintering additive via the conventional solid‐state reaction route. These results suggest that β‐spodumene ceramics sintered with Li₂O–GeO₂ sintering additive has a potential use as LTCC for multichip modules.     

Liquid‐phase sintering of highly Na+ ion conducting Na3Zr2Si2PO12 ceramics using Na3BO3 additive

Na₃Zr₂Si₂PO₁₂ (NASICON) is a promising material as a solid electrolyte for all‐solid‐state sodium batteries. Nevertheless, one challenge for the application of NASICON in batteries is their high sintering temperature above 1200°C, which can lead to volatilization of light elements and undesirable side reactions with electrode materials at such high temperatures. In this study, liquid‐phase sintering of NASICON with a Na₃BO₃ (NBO) additive was performed for the first time to lower the NASICON sintering temperature. A dense NASICON‐based ceramic was successfully obtained by sintering at 900°C with 4.8 wt% NBO. This liquid‐phase sintered NASICON ceramic exhibited high total conductivity of ~1 × 10^?3 S cm^?1 at room temperature and low conduction activation energy of 28 kJ mol^?1. Since the room‐temperature conductivity is identical to that of conventional high‐temperature‐sintered NASICON, NBO was demonstrated as a good liquid‐phase sintering additive for NASICON solid electrolyte. In the NASICON with 4.8 wt% NBO ceramic, most of the NASICON grains directly bonded with each other and some submicron sodium borates segregated in particulate form without full penetration to NASICON grain boundaries. This characteristic composite microstructure contributed to the high conductivity of the liquid‐phase sintered NASICON.     

Synthesis and sodium ionic conductivity for perovskite-structured Na0.25La0.25NbO3 ceramic

In this work, a perovskite-structured sodium ion conductor, Na_0.25La_0.25NbO₃ (NLNO) was developed from analogous Li_0.25La_0.25NbO₃ ceramic. NLNO ceramic was successfully synthesized by solid state reaction. The sodium ionic conduction in Na_0.25La_0.25NbO₃ ceramic was studied and the effect of sintering temperature on the microstructure, phase structure, density and sodium ionic conductivity for Na_0.25La_0.25NbO₃ was also discussed. Single phase of perovskite was successfully obtained from NLNO sintered at 1200 °C and 1250 °C, and the result shows high sintering temperature leads to a large grain size, large lattice parameters and high density. With an increase of sintering temperature from 1150 °C to 1250 °C, the conductivity of samples increases gradually. NLNO sintered at 1250 °C presents a high sodium ionic conductivity of 1.06 × 10^?5 S cm^?1 at 30 °C, which is much higher than that of electronic conductivity in NLNO sintered at 1250 °C.     

Flame Spray Synthesis of BaZr0.8Y0.2O3–δ Electrolyte Nanopowders for Intermediate Temperature Proton Conducting Fuel Cells

Flame Spray Synthesis (FSS) technique has been used for the preparation of BaZr_0.8Y_0.2O_3–δ (BZY20) nanoprecursors. The nanoprecursors were composed of a perovskite phase mixed with doped Zirconia and barium nitrate. Pure phase powder could be obtained after calcining the precursors at 1,200 °C. Both nanoprecursors and pure phase powder were then sintered at 1,600 °C to obtain dense specimen. AC impedance spectroscopy performed on the sintered samples allowed correlation of the electrical properties of the samples to their microstructures. The sintered nanoprecursors compared with the sintered pure phase powders showed enhanced grain growth associated with higher grain boundary conductivity. The influence of the reactive sintering on the enhanced grain growth and electrical properties in the nanoprecursors is discussed. The high total proton conductivity measured (7.7·10⁻³ S cm⁻¹ at 450 °C) promotes FSS as an effective powder synthesis method for the preparation of BZY20 electrolyte material for proton conducting fuel cells operating in the intermediate temperature range.     

Grain Boundary Space Charge Effect and Proton Dynamics in Chemically Stable Perovskite‐Type Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3−δ (BSCZGY): A Case Study on Effect of Sintering Temperature

The present study reports the effect of sintering temperature on the proton dynamics of perovskite‐type Ba_0.5Sr_0.5Ce_0.6Zr_0.2Gd_0.1Y_0.1O_3?δ (BSCZGY) by establishing a co‐relation between the grain‐boundary (GB) space charge effect, electrical conductivity and dielectric loss of the BSCZGY samples sintered at 1300°C, 1400°C, and 1550°C for 20 h in air. Although, the GBs are the main source of resistance in BaZrO₃ based ceramic proton conductors, we show that the GB impedance disappeared above 450°C and 300°C, respectively, for BSCZGY samples sintered at 1300°C and 1400°C. Interestingly, the BSCZGY sample sintered at 1550°C showed absence of GB contribution to total conductivity even at 200°C. The GB electrostatic potential [?(0)] was found to vary between 0.35–0.38 V and 0.4–0.45 V, respectively, for the samples sintered at 1300°C and 1400°C at 200°C–300°C. The migration energy (E_m) of the protons was found to be 0.71, 0.65 and 0.58 eV for the sample sintered at 1300°C, 1400°C and 1550°C, respectively.     

Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization

In this research, p‐type Bi₂Te₃–75% Sb₂Te₃ thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK² was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values.     

Increased electrical conductivity and the mechanism of samarium‐doped ceria/Al2O3 nanocomposite electrolyte

To further enhance the electrical conductivity of doped ceria, the samarium‐doped ceria (SDC)/Al₂O₃ nanocomposites were prepared through sintering the coprecipitated powders in 1100°C‐1300°C. The grain sizes of all composites are less than 100 nm and decrease with alumina addition. Besides the main phases of SDC and Al₂O₃, the SmAlO₃ can precipitate in the composites if sintered at higher temperatures or for longer dwell time. The deviations of SDC diffraction peak positions demonstrate the solid solution of alumina into SDC lattice. The total electrical conductivities of the composites increase with alumina content until 30% alumina is added. The SDC/30%Al₂O₃ presents the higher total conductivity than the pure SDC by about five times. Specifically, the grain interior conductivity generally decreases with the alumina addition while the grain‐boundary conductivity increases with that. The introduction of the conductive SDC/Al₂O₃ interface can contribute to the rise of total conductivity, yet the excessive alumina addition also blocks the oxygen ion conduction. The SmAlO₃ precipitation is detrimental to the ion conduction for it consumes part of alumina and leads to the decrement in Sm concentration of SDC grain. Appropriate alumina addition not only enhances the conductivity of SDC but also lowers the material cost.     

Sintering behavior,structural phase transition,and microwave dielectric properties of La1‐xZnxTiNbO6‐x/2 ceramics

La_1‐xZn_xTiNbO_6‐x/2 (LZTN‐x) ceramics were prepared via a conventional solid‐state reaction route. The phase, microstructure, sintering behavior, and microwave dielectric properties have been systematically studied. The substitution of a small amount of Zn²⁺ for La³⁺ was found to effectively promote the sintering process of LTN ceramics. The corresponding sintering mechanism was believed to result from the formation of the lattice distortion and oxygen vacancies by means of comparative studies on La‐deficient LTN ceramics and 0.5 mol% ZnO added LTN ceramics (LTN+0.005ZnO). The resultant microwave dielectric properties of LTN ceramics were closely correlated with the sample density, compositions, and especially with the phase structure at room temperature which depended on the orthorhombic‐monoclinic phase transition temperature and the sintering temperature. A single orthorhombic LZTN‐0.03 ceramic sintered at 1200°C was achieved with good microwave dielectric properties of ε_r~63, Q×f~9600 GHz (@4.77 GHz) and τ_f ~105 ppm/°C. By comparison, a relatively high Q × f~80995 GHz (@7.40 GHz) together with ε_r~23, and τ_f ~?56 ppm/°C was obtained in monoclinic LTN+0.005ZnO ceramics sintered at 1350°C.     

Flash sintering of a three‐phase alumina,spinel, and yttria‐stabilized zirconia composite

Three‐phase ceramic composites constituted from equal volume fractions of α‐Al₂O₃, MgAl₂O₄ spinel, and cubic 8 mol% Y₂O₃‐stabilized ZrO₂ (8YSZ) were flash‐sintered under the influence of DC electric fields. The temperature for the onset of rapid densification (flash sintering) was measured using a constant heating rate at fields of 50‐500 V/cm. The experiments were carried out by heating the furnace at a constant rate. Flash sintering occurred at a furnace temperature of 1350°C at a field of 100 V/cm, which dropped to 1150°C at a field of 500 V/cm. The sintered densities ranged from 90% to 96%. Higher electric fields inhibited grain growth due to the lowering of the flash temperature and an accelerated sintering rate. During flash sintering, alumina reacted with the spinel phase to form a high‐alumina spinel solid solution, identified by electron dispersive spectroscopy and from a decrease in the spinel lattice parameter as measured by X‐ray diffraction. It is proposed that the solid solution reaction was promoted by a combination of electrical field and Joule heating.     

High‐Temperature Electrical Conductivity of LaCr1−xCoxO3 Ceramics

LaCr_1?xCo_xO₃ solid‐solution ceramics (x = 0.0–0.3) were prepared by pressureless sintering of a submicrometer powder. The powder was synthesized by a modified glycine nitrate process at 800°C. The electrical conductivity of the material sintered at 1600°C was measured by AC four‐wire method from room temperature to 1200°C. While undoped (x = 0) LaCrO₃ revealed semiconductivity dominated by thermally activated mobility of small polarons over a vast temperature range, substitution of Co for Cr gave rise for a pronounced enhancement of conductivity at temperatures >200°C. XPS analysis showed that the concentration of Cr⁴⁺ on the Cr‐site and Co²⁺ at the Co‐site increased with Co substitution suggesting a thermally activated redox reaction Cr³⁺ + Co³⁺→Cr⁴⁺ + Co²⁺ to create additional charge carriers. Thus, Co doping offers a high potential for designing the electrical conductivity making LaCr_1?xCo_xO₃ an interesting resistivity material for high temperature applications.     

Effect of Sintering Additives on Relative Density and Li‐ion Conductivity of Nb‐Doped Li7La3ZrO12 Solid Electrolyte

Lithium ion conductors with garnet‐type structure are promising candidates for applications in all solid‐state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li⁺ conductivity (10^?3–10^?4 S/cm). Producing densified Li‐ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li‐ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li₇La₃ZrNbO₁₂ at sintering temperature of 900°C. Glasses in the LiO₂‐B₂O₃‐SiO₂‐CaO‐Al₂O₃ (LBSCA) and BaO‐B₂O₃‐SiO₂‐CaO‐Al₂O₃ (BBSCA) system with low softening temperature (<700°C) were used to modify the grain‐boundary resistance during sintering process. Lithium compounds with low melting point (<850°C) such as LiF, Li₂CO₃, and LiOH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85–92%, whereas those of lithium compounds were 62–77%. Li₇La₃ZrNbO₁₂ sintered with 4 wt% of LBSCA at 900°C for 10 h achieved a rather high relative density of 85% and total Li‐ion conductivity of 0.8 × 10^?4 S/cm at room temperature (30°C).     

Carbon nanotube/graphene oxide‐added CaO‐B2O3‐SiO2 glass/Al2O3 composite as substrate for chip‐type supercapacitor

A CaO‐B₂O₃‐SiO₂ (CBS) glass/40 wt% Al₂O₃ composite sintered at 900°C exhibited a dense microstructure with a low porosity of 0.21%. This composite contained Al₂O₃ and anorthite phases, but pure glass sintered at 900°C has small quantities of wollastonite and diopside phases. This composite was measured to have a high bending strength of 323 MPa and thermal conductivity of 3.75 W/(mK). The thermal conductivity increased when the composite was annealed at 850°C after sintering at 900°C, because of the increase in the amount of the anorthite phase. 0.25 wt% graphene oxide and 0.75 wt% multi‐wall carbon nanotubes were added to the CBS/40 wt% Al₂O₃ composite to further enhance the thermal conductivity and bending strength. The specimen sintered at 900°C and subsequently annealed at 850°C exhibited a large bending strength of 420 MPa and thermal conductivity of 5.51 W/(mK), indicating that it would be a highly effective substrate for a chip‐type supercapacitor.     

Sintering behavior of calcium lanthanum sulfide ceramics in field‐assisted consolidation

In this study, calcium lanthanum sulfide (CaLa₂S₄, CLS) ceramics with the cubic thorium phosphate structure were sintered at different temperatures by field‐assisted sintering technique (FAST). Densification behavior and grain growth kinetics were studied through densification curves and microstructural characterizations. It was determined that the densification in the 850°C‐950°C temperature range was controlled by a mixture of lattice or grain‐boundary diffusion, and grain‐boundary sliding. It was revealed that grain‐boundary diffusion was the main mechanism controlling the grain growth between 950°C and 1100°C. The infrared (IR) transmittance of the FAST‐sintered CLS ceramics was measured and observed to reach a maximum of 48.1% at 9.2 μm in ceramic sintered at 1000°C. In addition, it was observed that the hardness of the CLS ceramics first increased with increasing temperature due to densification, and then decreased due to a decrease in dislocations associated with grain growth.     

Nano–Nano Composite Powders of Lanthanum Zirconate and Yttria‐Stabilized Zirconia by Spray Pyrolysis

Powders composing of La₂Zr₂O₇ (LZ) and (Zr_0.8Y_0.2)O_1.9 (10YSZ) phases (volume ratio = 1:1) were synthesized by using a sol‐spray pyrolysis method. The effects of annealing temperature on the grain size and lattice parameter of the LZ–10YSZ powders were investigated. XRD results showed that the grain size of LZ and 10YSZ phases gradually grew from 10 to 95 nm and from 5 to 65 nm as the annealing temperature elevated from 900°C to 1200°C. The relative decreasing percentage of grain size comparing to that of the single‐phase LZ and 10YSZ powders were in the range 9%–36% and 37%–86%. The activation energy for grain growth of LZ and 10YSZ phases in the composite powders were 225 ± 12 and 382 ± 17 kJ/mol, which were 20% and 183% higher than that of the single‐phase counterparts. Obvious lattice contraction and lattice expansion for LZ and 10YSZ phases were observed at temperatures below 1100°C, respectively. SEM results revealed that LZ and 10YSZ phases were homogeneously distributed in the sintered bulk. The TEM results suggested that the grain growth was affected by the interaction on nanometer length scales of grain boundaries between LZ and 10YSZ phases in the composite.     

Fabrication and Performance of Solid Oxide Fuel Cells with La0.2Sr0.7TiO3–δ as Anode Support and La2NiO4+δ as Cathode

A novel fabrication process for solid oxide fuel cells (SOFCs) with La_0.2Sr_0.7TiO_3–δ (LST_A–) as anode support and La₂NiO_4+δ (LNO) as cathode material, which avoids complicated impregnation process, is designed and investigated. The LST_A– anode‐supported half cells are reduced at 1,200 °C in hydrogen atmosphere. Subsequently, the LNO cathode is sintered on the YSZ electrolyte at 1,200 °C in nitrogen atmosphere and then annealed in situ at 850 °C in air. The results of XRD analysis and electrical conductivity measurement indicate that the structure and electrochemical characteristics of LNO appear similar before and after the sintering processes of the cathode. By using La_0.6Sr_0.4CoO_3–δ (LSC) as current collector, the cell with LNO cathode sintered in nitrogen atmosphere exhibits the power density at 0.7 V of 235 mW cm⁻² at 800 °C. The ohmic resistance (R_S) and polarization resistance (R_P) are 0.373 and 0.452 Ω cm², respectively. Compared to that of the cell with the LNO cathode sintered in air, the sintering processes of the cell with the LNO cathode sintered in nitrogen atmosphere can result in better electrochemical performance of the cell mainly due to the decrease in R_S. The microstructures of the cells reveal a good adhesion between each layer.     

Selective Corrosion Preparation and Sintering of Disperse α‐Al2O3 Nanoparticles

Disperse fine equiaxed α‐Al₂O₃ nanoparticles with a mean particle size of 9 nm and a narrow size distribution of 2–27 nm were synthesized using α‐Fe₂O₃ as seeds and isolation via homogeneous precipitation‐calcination‐selective corrosion processing. The presence of α‐Fe₂O₃ acting as seeds and isolation phase can reduce the formation temperature to 700°C and prevent agglomeration and growth of α‐Al₂O₃ nanoparticles, resulting in disperse fine equiaxed α‐Al₂O₃ nanoparticles. These α‐Al₂O₃ nanoparticles were pressed into green compacts at 500 MPa and sintered first by normal sintering to study their sintering behavior and finally by two‐step sintering (heated to 1175°C without hold and decreased to 1025°C with a 20 h hold in air) to obtain nanocrystalline α‐Al₂O₃ ceramics. The two‐step sintered bodies are nanocrystalline α‐Al₂O₃ with an average grain size of 55 nm and a relative density of 99.6%. The almost fully dense nanocrystalline α‐Al₂O₃ ceramic with finest grains achieved so far by pressureless sintering reveals that these α‐Al₂O₃ nanoparticles have an excellent sintering activity.     

Crystal structure,defect relaxation,and microwave dielectric properties of Ba[(Mg1/3Nb2/3)1−xHfx]O3 solid solutions

Ba[(Mg_1/3Nb_2/3)_1?xHf_x]O₃ (BMNH, x = 0.05, 0.1, 0.15, 0.2) solid solutions were prepared via the solid‐state reaction method. The effect of BaHfO₃ on the crystal structure, microwave dielectric performance, and defect relaxation behavior of Ba(Mg_1/3Nb_2/3)O₃ (BMN) were studied. BaHfO₃ additions degraded the sintering activity of BMN powder, requiring a high sintering temperature (T_s) ~ 1650°C; but it could be effectively improved by a prolonged sintering process at a lower T_s of 1600°C. The well‐sintered BMNH ceramics (1600°C for 30 h) possessed a high densification >96%, and exhibited cubic perovskite structures without 1:2 cation ordering. Once doped with Hf, the low‐temperature relaxation in dielectric spectroscopy and thermally stimulated depolarization current (TSDC) for pure BMN disappeared, further indicating such relaxation is related to cation‐ordered structure. Oxygen vacancies, namely showing in‐grain and across‐grain‐boundary relaxation of ‐related defects, were the main defect types in BMNH. The concentrations of in‐grain decreased as x increased, which is beneficial to BMNH to maintain high Q × f values of 69 400‐73 000 GHz. Accompanied by a high ε_r of 33.27‐33.59 and a low τ_f of +13.6 to +20.7 ppm/°C, these materials have a good potential for applications in microwave components and devices.     

New Methods for Preparing Submicrometer Powders of The Tungstate‐Ion Conductor Sc2(WO4)3 and its Al and In Analogs

Two new methods for preparing submicrometer powders of M₂(WO₄)₃, M = Sc, In, and Al via combustion synthesis are reported. Stoichiometric combinations of trivalent metal nitrates, ammonium metatungstate, and either urea or carbohydrazide as the fuel were reacted at 550°C, producing amorphous or poorly crystallized powders with an average particle size ranging from 164 to 350 nm. Calcining the powders at 800°C for 1 h produced well‐crystallized, phase‐pure powders with an average particle size ranging from 210 to 711 nm. Powders sintered at 1000°C for 14 h resulted in pellets that were 87%–95% of the theoretical density, which is notably higher than typically obtained from powders prepared by solid‐state reaction. Whereas there was little difference in the microstructure of Al₂(WO₄)₃ pellets prepared with the two different powders, the carbohydrazide‐derived powders resulted in In₂(WO₄)₃ and Sc₂(WO₄)₃ pellets with a larger grain size than those prepared with urea‐derived powders. The electrical conductivity of the sintered pellets, while comparable to that reported for polycrystalline M₂(WO₄)₃ prepared by solid‐state reaction, was strongly influenced by grain‐boundary effects.     

Influence of processing conditions on the ionic conductivity of holmium zirconate (Ho2Zr2O7)

Nanopowders of holmium zirconate (Ho₂Zr₂O₇) synthesised through carbon neutral sol-gel method were pressed into pellets and individually sintered for 2 h in a single step sintering (SSS) process from 1100 °C to 1500 °C at 100 °C interval and in a two step sintering (TSS) process at (I) −1500 °C for 5 min followed by (II) - 1300 °C for 96 h. Relative density of each of the sintered pellet was determined using the Archimedes’ technique and the theoretical density was calculated from crystal structure data. Grain size was obtained from SEM micrographs using ImageJ. Pellets processed by TSS have been found to be denser (98 %) with less grain growth (1.29 μm) as compared to the pellets processed using SSS process. Ionic conductivity of Ho₂Zr₂O₇ pellets sintered by two different processes was measured using ac impedance spectroscopy technique over the temperature range of 350 °C–750 °C in the frequency range of 100 mHz–100 MHz for both heating and cooling cycles. The temperature dependence of bulk (2.67⨯10⁻³ Scm⁻¹) and grain boundary (2.50⨯10⁻³ Scm⁻¹) conductivities of Ho₂Zr₂O₇ prepared by TSS process are greater than those processed by SSS process suggesting the strong influence of processing conditions and grain size. Results of this study, indicates that the TSS is the preferable route for processing the holmium zirconate as it can be sintered to exceptionally high densities at lower temperature, exhibits less grain growth and enhanced ionic conductivity compared with the samples processed by SSS process. Hence, holmium zirconate can be considered as a promising new oxide ion conducting solid electrolyte for intermediate temperature SOFC applications between 350 °C and 750 °C temperature range.     

Impedance Spectroscopy and Dielectric Properties of Flash Versus Conventionally Sintered Yttria‐Doped Zirconia Electroceramics Viewed at the Microstructural Level

The defect chemistry‐modulated dielectric properties of dense yttria‐doped zirconia ceramics prepared by conventional sintering (at 1350°C–1500°C) and electric field‐assisted flash sintering (55 V/cm at 900°C) were studied by impedance spectroscopy. While the bulk dielectric properties from both sets of samples showed only small and insignificant changes in conductivity and permittivity, respectively, a huge increase of these properties was measured for the grain boundaries in the flash sintered specimens. A close analysis of these results suggests that flash sintering reduced grain‐boundary thickness (by about 30%), while increasing the concentration of oxygen vacancies near these interfaces (by about 49%). The underlying mechanism proposed is electric field‐assisted generation and accommodation of defects in the space‐charge layers adjacent to the grain surface. The changes in measured permittivity are attributed to the boundary thickness effect on capacitance, while conductivity involved variations in its defect density‐dependent intrinsic value, accounting for changes also observed in grain‐boundary relaxation frequencies. Therefore, in terms of modifications to the specific dielectric properties of these materials, the overall consequence of flash sintering was to considerably lower the semi‐blocking character of the grain boundaries.