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The inhomogeneous composition distribution of atmospheric plasma sprayed La 2 Ce 2 O 7 limits its operation in thermal barrier coatings. Two types of La 2 Ce 2 O 7 powders were used to investigate the effect of the powder size and structure on the preferential evaporation of Ce during plasma spraying. The results indicate that powder particle size is dominant for the Ce evaporation loss. Such effect is significantly intensified with the decrease of particle size. When the particle size is larger than 30 μm, the Ce loss is less or can be neglected. Two mechanisms including the element diffusion mechanism and convection mass transfer mechanism are proposed to well explain the evaporation rule. Moreover, the loss of Ce is higher using the agglomerate-sintered powder due to its higher thermal conductivity than the as-agglomerated powder. Correspondingly, the CeO 2 loss can be neglected in the coatings as the agglomerated powders with a size <30 μm were used. [ABSTRACT FROM AUTHOR]

La-doped SrTiO 3 (La x Sr 1−x TiO 3 , LST), as the promising ceramic-based interconnect material, usually needs to be sintered in reductive atmosphere at a temperature ≥ 1450 °C, such sintering condition is not friendly to cell fabrication and application. To reduce the sintering temperature of air-sintered LST, seven sintering additives, Bi 2 O 3 , Fe 2 O 3 , Li 2 O, MnO 2 , NiO, V 2 O 5 , and Co 3 O 4 , are added to the LST in this work. The results show that only Co 3 O 4 is conductive to remarkable sintering at the temperatures of 1250 °C. The relative density of LST-3%Co 3 O 4 reaches 92%, while that of the pure LST is only 48%. Moreover, the conductivity of LST-3%Co 3 O 4 achieves 8.2 S/cm at 800 °C in humidified hydrogen, which exceed 5.5 times that of the pure LST. Interestingly, LST-3%Co 3 O 4 exhibits an average TEC of 11.5 × 10−6 K−1 between 400 and 900 °C, which is very close to that of other components of SOCs. • Co 3 O 4 addition promotes the remarkable sintering of LST at a low temperature of 1250 °C. • The relative density of LST-3%Co 3 O 4 sintered at 1250 °C achieves 94.3%. • The conductivity of air-sintered LST-3%Co 3 O 4 in wet H 2 environment at 800 °C reaches 8.2 S/cm. • LST-3%Co 3 O 4 shows a matched TEC of ∼11.5 × 10−6 K−1 at 400-900 °C. [ABSTRACT FROM AUTHOR]

To achieve a coating density meeting the solid oxide fuel cell (SOFC) electrolyte requirements of high gas tightness and ionic conductivity, in this study, a new interface healing densification process based on a liquid-phase sintering induction mechanism was conducted on plasma-sprayed 8 mol% Y 2 O 3 -stabilized ZrO 2 (8YSZ) coatings. Using Fe 2 O 3 and Bi 2 O 3 as healing additives, metallurgical healing of unbound interfaces was achieved by impregnating the additives into the gap interfaces, followed by liquid-phase sintering at 1200 and 1050 °C. After healing, the YSZ coating exhibited a dense bulk-like microstructure with a significant reduction in the gas leakage rate by two orders of magnitude, and the oxygen ion conductivity of the coating was significantly increased. The YSZ coating healed with the Fe 2 O 3 additive showed an oxygen ionic conductivity nearly one order of magnitude higher than that of the as-sprayed coating, reaching more than 80% of the value of the high-temperature-sintered YSZ bulk. • A new interface healing process based on liquid-phase sintering was conducted on APS YSZ coatings. • The interface-healed YSZ coating exhibited a dense bulk-like microstructure. • The gas leakage rate of the interface-healed YSZ coating decreased by two orders of magnitude. • Ionic conductivity of the interface-healed YSZ coating reached > 80% of the sintered bulk. • The cell assembled with interface-healed YSZ-Fe 2 O 3 electrolyte achieved MPD of 1.04 W/cm2 at 800 °C. [ABSTRACT FROM AUTHOR]

Developed ceramic capacitors with excellent recoverable energy storage density (W rec) and efficiency (η) are greatly desired for next-generation pulsed power devices but challenge as well. Herein, outstanding W rec of 5.2 J/cm3 and η of 82% are achieved in the PbO-doped fine grain Bi 0.25 Na 0.25 Sr 0.5 TiO 3 (BNST-P) based relaxor ferroelectric ceramics. The corresponding mechanism is that A-site Pb-doping increases maximum polarization and breakdown strength, and suppresses remnant polarization simultaneously. Meanwhile, the energy storage property possesses excellent temperature and frequency stability, and the variation of W rec and η is less than 5% within the range of 25–100 °C and 2–100 Hz. Encouragingly, superior charge-discharge performance with fast discharge speed t 0.9 of 24 ns and high power density P D of 296 MW/cm3 is obtained. These striking comprehensive results suggest BNST-P ceramics possess potential prospects for applications. [ABSTRACT FROM AUTHOR]

Recently, SrTi 0.3 Fe 0.7 O 3−δ (STF) has been investigated as a highly stable oxygen electrode material for solid oxide electrochemical cells (SOCs) with a sufficiently low resistance for cell operation at temperatures of > 700 °C. However, in general, the STF electrode performance is limited at temperatures of ≤ 700 °C due to the low oxygen surface exchange coefficient, which is mainly caused by high Sr surface segregation. To improve the electrode performance, Sr 0.9 (Ti 0.3 Fe 0.7)O 3−δ (A-STF) with an A-site-deficient design is developed to reduce the Sr content and thus reduce the Sr surface segregation, thereby providing a unique combination of excellent oxygen electrode performance and long-term stability. The A-site deficiency reduces the electrode polarization resistance by > 3 times at 600 °C and clearly improves the oxygen diffusion and surface exchange coefficients due to the decrease of Sr surface segregation. The A-STF electrode exhibits stable performance in the fuel cell and electrolysis modes at 1 A cm−2 > 1200 h. The stability of STF-based oxygen electrodes in a CO 2 -enriched atmosphere is investigated, and the results indicate that A-STF exhibits excellent CO 2 tolerance. • A-STF is successfully applied as high-performance oxygen electrode for SOCs. • A factor of > 3 reduction in polarization resistance by A-site deficient design. • A factor of > 2 improvement in single cell performance by using A-STF electrode. • No measurable degradation observed during 1200-h life tests for A-STF. • Excellent CO 2 tolerance with no variation in R p with time even in 10% CO 2 -air. [ABSTRACT FROM AUTHOR]

Grain-oriented Pb(Mg 1/3 Nb 2/3)O 3 -PbZrO 3 -PbTiO 3 (PMN-PZ-PT) based ceramics were synthesized through templated grain growth via using BaTiO 3 (BT) templates. Although BT templates are partially destroyed by PMN-PZ-PT matrix, CuO addition remarkably promotes [001] c -oriented grain growth behavior of the ceramics, resulting in an improvement of Lotgering factor F 001 from ~86% to 98%. Both crystallographic texture and CuO doping increase tetragonality and reduce average domain size of the ceramics dominated by rhombohedral phase. Consequently, 0.50 wt% CuO-doped ceramics (F 001 ~98%) exhibit optimum electromechanical properties: d 33 ~860 pC/N, d 33 × g 33 ~48.6 × 10−12 m2/N, k p ~0.80, E c ~7.2 kV/cm, tan δ ~0.8% and T c ~222 °C. In addition to ~3.7 times and 6.6 times higher d 33 and d 33 × g 33 , those ceramics possess about 240% enhanced piezoelectric strain and much better thermal stability (S max / E max variation ≤2% between RT and 150 °C) relative to non-textured counterpart. This work offers a good paradigm for simultaneously exploring high piezoelectric response and good temperature stability in piezoceramics, benefiting the development of next-generation advanced electromechanical devices. [ABSTRACT FROM AUTHOR]

Solid solution ceramics of (1- x)Sr 0.75 Ba 0.25 Nb 2 O 6 - x PbZr 0.52 Ti 0.48 O 3 (x = 0−0.4) were prepared and investigated. The phase evolves from tungsten bronze for x = 0, coexisted tungsten bronze and pyrochlore at x = 0.3, to pyrochlore for x > 0.3. As the results, the ceramics show dramatically composition dependent microstructure and electrical property. The grain shape changes from anisotropic pillar-like with maximum length-diameter ratio of 3.3 at x = 0.2 to isotropic cubic-like for x > 0.2. At the same time, the maximum dielectric constant temperature tends to decrease with an exceptional increase at x = 0.3 due to the coexisted phases. Interestingly, the x = 0.3 ceramic endures ultrahigh breakdown strength of 340 kV/cm, which, together with enhanced polarization, results in maximum recoverable energy storage density of 3.0 J/cm3and energy storage efficiency of 81.5 % at room temperature. [ABSTRACT FROM AUTHOR]

(1- x)(Pb 0.97 La 0.02)(Zr 0.5 Sn 0.4 Ti 0.1)O 3 - x (Na 0.5 Bi 0.5) 0.94 Ba 0.06 TiO 3 (x = 0 ∼ 0.4) ceramics have been prepared and investigated. The ceramics consist of perovskite solid solution matrix and precipitated, isolated SnO 2 particle, resulting in 0–3 type composite structure. With increasing x value, the room temperature crystal structure of perovskite solid solution transforms from tetragonal to pseudocubic, therefore, the electrical property evaluates form robust antiferroelectric at x = 0, metastable antiferroelectric at x = 0.1, and then relaxor ferroelectric at x > 0.1. Moreover, the breakdown strength is enhanced due to the composite structure and reaches maximum value of 190 kV/cm at x = 0.2. Both the phase transition and enhanced breakdown strength are helpful to improve energy storage property, the x = 0.2 ceramic shows largest recoverable energy density w rec of 1.84 J/cm3, discharge efficiency η of 86.6 %. Especially, both w rec and η illustrates significantly improved thermal stability within 25−125 °C. [ABSTRACT FROM AUTHOR]

Composite ceramics based on non-stoichiometric 0.94Na 0.48 Bi 0.44 TiO 3 (NBT-BT) and ZnO, (1- x)NBT-BT: x ZnO with x = 0 ∼ 0.3 are prepared and investigated. The phase structure changes from tetragonal-dominated for x = 0 to rhombohedral-dominated for x > 0. The domain structure simultaneously evolves from nanodomain to macrodomain. At room temperature, the x = 0 ceramic has a pinched polarisation-electric field (P-E) loop, whereas x > 0 ceramics demonstrate square-shaped P-E loops with a maximum P r of 30.6 μC/cm2 of x = 0.2. Moreover, ceramics with x = 0.1 and 0.2 have enhanced pyroelectric coefficients in a wide temperature range with full width at half maximums of 31 °C and 15.5 °C and peak values of 29.2 × 10−4 and 100.7 × 10−4 C/(m2·K), respectively. The results are explained based on the stress-induced room temperature relaxor-ferroelectric transition. This work affirms that forming composites is an effective way to tune the electrical properties of NBT-based materials. [ABSTRACT FROM AUTHOR]

Unquenched and quenched ceramics of 0.85Na 0.5 Bi 0.5 TiO 3 -0.11K 0.5 Bi 0.5 TiO 3 -0.04BaTiO 3 have been prepared, and their crystal structure, temperature-dependent ferro-/piezoelectric properties and domain structure have been comparatively investigated. It is shown that quenching process can significantly improve the ferroelectric-relaxor transition temperature (T F-R), which is 130 °C for unquenched ceramics and 198 °C for quenched one. As the result, the thermal stability of ferro-/piezoelectric properties is highly enhanced. These observations are mainly attributed to the quenching induced stable rhombohedral ferroelectric phase and the defect altered domain evolution. This work may deepen the understanding of the effect of quenching on crystal structure, domain structure and their contributions to thermal stability of NBT-based ceramics. [ABSTRACT FROM AUTHOR]

Highlights • A new ceramic by introducing Bi(Mn 0.5 Ti 0.5)TiO 3 into 0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 is prepared via solid state reaction method. • The compositions within x = 0.03–0.055 exhibit large strain of 0.31% ˜0.41% and electrostrictive coefficient of 0.027–0.041 m4/C2. • At x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. Abstract (1- x)[0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 ]- x Bi(Mn 0.5 Ti 0.5)O 3 (x = 0–0.06, BNKMT100 x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn 0.5 Ti 0.5)O 3 induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03–0.055 exhibit large strain of 0.31%–0.41% and electrostrictive coefficient of 0.027–0.041 m4/C2. Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25–100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn 0.5 Ti 0.5)O 3. [ABSTRACT FROM AUTHOR]

0.82[0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 ]-0.18K 0.5 Na 0.5 NbO 3 : x ZnO (BNT-BT-KNN: x ZnO, x  = 0-0.40) relaxor composites were prepared and their electrical properties were investigated. The breakdown electric field increases with increasing ZnO content. For x  = 0 and x  = 0.40 samples, the maximum recoverable energy storage density is 0.74 J/cm 3 and 1.03 J/cm 3 while the maximum energy storage efficiency is 86.7% and 72.7% under the electric field of 9.0 kV/mm and 14.0 kV/mm, respectively. The recoverable energy storage density and efficiency of the composite vary less than 2.5% from 25 °C to 125 °C, which indicates temperature-insensitive energy storage performance. These results are discussed based on the ZnO-enhanced bulk resistivity and the ZnO-induced local electric field which suppresses the evolution of polar nanoregions. [ABSTRACT FROM AUTHOR]

Further improving electromechanical properties and overcoming relatively low Curie temperature ( T c ) of (1- x )Pb(Mg 1/3 Nb 2/3 )O 3 - x PbTiO 3 (PMN-100 x PT) are still two scientific issues. Here, we demonstrate a stable coexistence of monoclinic-tetragonal (M C -T) phases in ZnO-modified PMN-32PT (PMN-32PT: x ZnO) due to the diffusion-induced substitution of Zn 2+ for Mg 2+ . The Curie temperature, saturated polarization, remnant polarization, piezoelectric coefficient ( T c , P s , P r , d 33 ) are increased from (160 °C, 22.0 μC/cm 2 , 13.3 μC/cm 2 , 350 pC/N) for x = 0 to (180 °C, 30.3 μC/cm 2 , 22.4 μC/cm 2 , 470 pC/N) for x = 0.06. Moreover, the thermal stability is improved. After annealing at 150 °C, the x = 0.06 sample shows retrained d 33 value of 209 pC/N, about 4 times larger than that of x = 0 counterpart. The improved properties are attributed to the substituting increased polar nanoregions and easy domain switching in M C phase. [ABSTRACT FROM AUTHOR]

How to obtain dense La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 (LSGM) electrolyte at low sintering temperature (<1300 °C) is a challenge to improve solid oxide fuel cell (SOFC) performance at intermediate operation temperature. In this study, a double-layer design method for vacuum cold spray (VCS) prepared-LSGM electrolyte assisted with two-step sintering at a low temperature was proposed. The sintering behavior of VCS deposited LSGM layers at 1200 °C was investigated. The LSGM layers became denser in most regions except the appearance of some cracks. Subsequently, the effect of a second LSGM layer on the sintered top layer was studied to block cracks. Results showed that the co-sintered layer with a thickness of approximately 5 μm presented a maximum open circuit voltage of ∼0.956 V at 650 °C and a maximum power density of 592 mW/cm 2 at 750 °C. Result indicates that the sintering assisted VCS is a promising method to prepare the LSGM electrolyte applied in intermediate temperature SOFCs. [ABSTRACT FROM AUTHOR]