Sc2O3 Doping Research Articles

Effect of Sc2O3 doping on YSZ TBCs: Morphologies, phase composition, mechanical properties, and high-temperature oxidation resistance

Y2O3 stabilized ZrO2 thermal barrier coatings (YSZ TBCs) and Sc2O3 and Y2O3 co-stabilized ZrO2 thermal barrier coatings (ScYSZ TBCs) were prepared by atmospheric plasma spraying technology, and then a high-temperature oxidation experiment was carried out at 1100 °C. Whereupon the morphologies, phase composition, and mechanical properties of YSZ ceramic coating and ScYSZ ceramic coating after different high-temperature oxidation time, as well as the high-temperature oxidation resistance of YSZ TBCs and ScYSZ TBCs, were comparatively studied. The results showed that after high-temperature oxidation, ScYSZ ceramic coating presented slighter cracking and exhibited better sintering resistance. After high-temperature oxidation, the phase composition of both YSZ ceramic coating and ScYSZ ceramic coating was still a single T' phase, and their interplanar spacing became larger; nevertheless, the interplanar spacing of ScYSZ ceramic coating was smaller than that of YSZ ceramic coating. After high-temperature oxidation, ScYSZ ceramic coating had higher hardness, smaller elastic modulus, and smaller fracture toughness. In addition, ScYSZ TBCs exhibited better high-temperature oxidation resistance according to the morphology, equivalent thickness, high-temperature oxidation kinetics, and high-temperature oxidation thermodynamics of TGO.

Effect of Sc2O3 doping on the microstructure and electrical characteristics of ZnO linear resistors

Herein, to improve the electrical characteristics, ZnO linear resistors mixed with MgO, TiO2, Al2O3, and various concentrations of Sc2O3 (with 0, 0.35, 0.7, and 1.05 wt %) were obtained using the conventional solid-state sintering technique, while the influences of Sc2O3 doping on the micro-morphology and electrical characteristics was investigated in detail. The crystalline phases and microstructure were investigated by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The dielectric properties and electrical characteristics were evaluated using a precision inductance-capacitance-resistance meter and a high-voltage source meter. Results from SEM micrographs, XRD patterns, and EDS mappings illustrated that the doping of Sc2O3 hinders the growth of ZnO grains. Electric field-current density and resistivity-frequency measurements illustrated that the doping of Sc2O3 improves the linear performance of ZnO linear resistors and increases its grain resistivity and grain boundary resistivity. With Sc2O3 doping, the dielectric properties of the samples are significantly affected, while the resistance-temperature features reveal the negative temperature constant function. By appropriate Sc2O3 doping, the ZnO linear resistors exhibited excellent performance with grain boundary barrier height φb of 0.0106 eV, nonlinear coefficient α of 1.03, and resistance temperature constant αT of −2.88 × 10−3. It is beneficial to investigate the influence of Sc2O3 doping on the micro-morphology and electrical performances in detail for the preparation of zinc oxide linear resistors with superior performance.

Effect of Sc2O3 doping on microstructure and electrical properties of ZnO–Bi2O3-based varistors

ZnO varistors are widely used in electrical systems. In this study, the effects of different contents of Sc2O3 doping on the microstructure and electrical properties of ZnO varistors were systematically analyzed. The results show that the doping of Sc2O3 is conducive to the uniform growth of the ZnO grains and improves the breakdown field strength of varistors. At the same time, Sc2O3 doping improves the barrier height of the varistors, resulting in a significant increase in nonlinear coefficient and a decrease in leakage current density. The sample doped with 0.15 mol% Sc2O3 exhibited excellent electrical properties with breakdown field strength of 696.13 V/mm, a leakage current density of 1.26 μA cm−2, and a nonlinear coefficient of 55.00. The Sc2O3 doped samples have good performance, which is of guiding significance for the study of other trivalent and tetravalent ion doping with a radius similar to that of Zn2+.

Effects of scandium oxide on domain structure, dielectric and ferroelectric properties of barium zirconate titanate ceramics

The Sc2O3 doped Ba(Zr0.1Ti0.9)O3 ferroelectric ceramics were fabricated by the conventional solid state reaction method. The influences of Sc2O3 on their microstructure, especially domain structure, dielectric and ferroelectric properties were investigated by X-ray diffractometer, scanning electron microscope, LCR measurement system and ferroelectric tester. The Sc2O3 doped Ba(Zr0.1Ti0.9)O3 ceramics are tetragonal perovskites with no impurity phases. The average grain size of Ba(Zr0.1Ti0.9)O3 ceramics decreases from ~40 µm to ~5 µm as the Sc2O3 content increases. Both the 90° ferroelectric domains and the 180° ones exist in the 0.2 mol% Sc2O3 doped Ba(Zr0.1Ti0.9)O3 ceramics with an average grain size of ~26 µm. The ferroelectric -paraelectric phase transition temperature and the dielectric permittivity maximum of Ba(Zr0.1Ti0.9)O3 ceramics decrease with increasing Sc2O3 doping content, while the temperature stability of relative dielectric constant is improved effectively after Sc2O3 modification in BZT ceramics. The remnant polarization and the coercive field of BZT ceramics decrease in Sc2O3 highly doped BZT ceramics as the Sc2O3 content increases.

Effect of doping CeO2 and Sc2O3 on structure, thermal properties and sintering resistance of YSZ

6-8 wt% yttria-stabilized zirconia (YSZ) has been widely employed as thermal barrier coating (TBC) to protect the high-temperature components of aero-engine and gas-turbine. However, the phase transition and sintering densification at high temperature seriously limit its application above 1200 °C. On account of this, CeO2 and Sc2O3 were doped into the YSZ by solid-state reaction sintering method in this paper. The effects of doping on the crystal structure, phase transition behavior and sintering resistance were investigated on the basis of XRD, Raman and FESEM, and the evolution of thermal properties of the ceramics was also analyzed. The results indicated that doped CeO2 increases the cell volume and tetragonal degree, but doped Sc2O3 was opposite. Co-doping caused not only significant difference in atomic mass and radius but also the formation of a large number of oxygen vacancies in the ceramics. Therefore, CeScYSZ showed the lowest thermal conductivity (1.53 W‧m−1‧K−1), which was about 23% lower than that of YSZ (2.00 W‧m−1‧K−1). More importantly, the oxygen vacancy also effectively stabilized the octet lattice, while the increase of lattice energy caused by Sc-O bond made it difficult for ions to misplace, which finally well prevented the transformation from t phase to m phase. There was no detrimental m-ZrO2 phase formation in the CeScYSZ after 120 h at 1500 °C. Besides, Co-doping could simultaneously overcome the poor sintering resistance caused by single CeO2 doping and the lower thermal expansion coefficient caused by single Sc2O3 doping, thus the CeScYSZ should be an ideal long-acting thermal protection material at higher temperatures.

Thermo-physical and mechanical properties of Yb2O3 and Sc2O3 co-doped Gd2Zr2O7 ceramics

Ceramic materials for the thermal barrier coating (TBC) application of Gd2Zr2O7 (GZO), (Gd0.94Yb0.06)2Zr2O7 (GYb0.06Z), (Gd0.925Sc0.075)2Zr2O7 (GSc0.075Z), (Gd0.865Sc0.075Yb0.06)2Zr2O7 (GSc0.075Yb0.06Z), and (Gd0.8Sc0.1Yb0.1)2Zr2O7 (GSc0.1Yb0.1Z) were successfully synthesized by chemical co-precipitation. The effects of the doping of Sc2O3 and Yb2O3 on the phases, thermo-physical and mechanical properties of the ceramics were investigated. The results show that both Yb2O3 and Sc2O3 doping promoted the phase transition of GZO from pyrochlore to fluorite. All the Sc2O3-doped samples exhibited enhanced fracture toughness, as compared to the undoped sample. Furthermore, the GSc0.075Yb0.06Z sample revealed a thermal conductivity of ~0.8 W/mK at 1200 °C, which was nearly 30% lower than that of the undoped sample. The associated mechanisms related to the effects of the doping on the thermophysical and mechanical properties are discussed.

Preparation and Electrochemical Properties of CaZr1-xScxO3-α

To develop a CaZrO3 -based, high-temperature proton conductor with high conductivity and resistance to the reduced atmosphere, we used Sc as a substitute for In as the dopant in CaZrO3. The electrical conductivity of CaZr1-xScxO3-α (x = 0.06, 0.12, 0.18, and 0.24) specimens was measured using the two-terminal ac method in an oxygen-rich atmosphere, hydrogen-rich atmosphere, and water vapor-rich atmosphere, at temperatures ranging from 573 K to 1473 K. The electrical conductivity of the CaZr1-xScxO3-α samples first increased and then decreased with the increase in amount of Sc2O3 doping, and it increased with an increase in temperature. The results of the H/D isotope effect measurement indicated that in the three different atmospheres, at temperatures from 573 K to 1273 K, protons are the dominant charge carrier. From the measurement of electromotive force, the theoretical (calculated) and the measured electromotive forces coincided. The proton mobility of CaZr1-xScxO3-α exceeded 90% in the hydrogen-rich atmosphere at temperatures from 573 K to 1273 K. At higher temperatures of 1373 K to 1473 K, positive holes were the dominant charge carrier in the oxygen-rich atmosphere, whereas the dominant charge carrier was vacancies in the hydrogen-rich atmosphere. These results agree with our previous studies.

Sc2O3 doped Bi2O3-ZnO thin films varistor prepared by sol-gel method

Sc2O3 modified Bi2O3-ZnO films varistors with different doping ratios were prepared by Sol-gel method. The result indicated that doping of Sc2O3 significantly enhance the nonlinear current-voltage (I-V) characteristics of Bi2O3-ZnO films. The highest non-linearity was obtained for 0.4mol% Sc content with the nonlinear coefficient α = 3.7 and 301 μA in leakage current. The grain size of ZnO phase firstly increased with Sc2O3 doping when the content of Sc2O3 is no more than 0.2 mol%. Upon the much more doping of Sc2O3, the growth of ZnO crystal was inhibited, leading to smaller grain size. The threshold voltage VT was inversely proportional with grain size of ZnO phase. Doping oxides gathered in the grain boundary significant impact on threshold voltage and leakage current.

Enhancement of Dielectric Breakdown Strength and Energy Conversion Efficiency of Niobate Glass-Ceramics by Sc2O3 Doping

Niobate glass-ceramics K2O-SrO-Nb2O5-B2O3-Al2O3-SiO2 (KSN-BAS) doped with different amounts of Sc2O3 have been prepared through a melt quenching/controlled crystallization method, and the influence of the Sc2O3 content on their phase composition, microstructure, dielectric performance, and charge–discharge properties investigated. X-ray powder diffraction results showed that the peak positions of the KSr2Nb5O15 phase shifted to higher angle and the glass-ceramic microstructures were significantly improved by Sc2O3 addition. Based on these results, 0.5 mol.% Sc2O3 doping was found to achieve remarkable enhancement in energy storage density, which reached 9.63 ± 0.39 J/cm3 at dielectric breakdown strength of 1450.38 ± 29.01 kV/cm with high conversion efficiency of ∼ 92.1%. For pulsed power applications, discharge speed of 17 ns and power density of 0.48 MW/cm3 were obtained in the glass-ceramic with 0.5 mol.% Sc2O3. These results could provide a new design strategy for high-performance dielectric capacitors.

Oxygen‐ion conduction in scandia‐stabilized zirconia‐ceria solid electrolyte (xSc2O3–1CeO2–(99−x)ZrO2, 5 ≤ x ≤ 11)

AbstractSolid oxide fuel cells (SOFCs) operating at intermediate temperature (500°C‐700°C) provide advantages of better durability, lower cost, and wider target application market. In this work, we have studied Sc2O3 (5‐11 mol%) stabilized ZrO2–CeO2 as a potential solid electrolyte for application in IT‐SOFCs. Lower Sc2O3 doping range than the traditional 11 mol% Sc2O3‐stabilized ZrO2 is an interesting research topic as it could potentially lead to an electrolyte with reduced oxygen vacancy ordering, lower cost, and higher mechanical strength. XRD and Raman spectroscopy was used to study the phase equilibrium in ZrO2–CeO2–Sc2O3 system and impedance spectroscopy was done to estimate the grain, grain boundary, and total ionic conductivities. Maximum for the grain and grain‐boundary conductivities as well as the tetragonal‐cubic phase boundary was found at 8‐9 Sc2O3 mol% in ZrO2‐1 mol% CeO2 system. It is suggested that the addition of 1 mol% CeO2 in the ZrO2 host lattice has improved the phase stability of high‐conductivity cubic and tetragonal phases at the expense of low‐conductivity t′‐ and β‐phases.

Phase structure evolution and thermal expansion variation of Sc2O3 doped Nd2Zr2O7 ceramics

Abstract (Nd1−xScx)2Zr2O7 (x = 0, 0.1, 0.3, 0.5, 0.7) compounds were synthesized by solid state reaction at 1700 °C for 10 h, and characterized by XRD, Raman spectroscopy, SEM and high-temperature dilatometer. Nd2Zr2O7 exhibited pyrochlore phase, and its lattice parameter increased after Sc2O3 doping, which could be attributed to the presence of Sc3+ interstitial ions in pyrochlore lattice. Fluorite phase formed in the doped Nd2Zr2O7, and (Nd0.3Sc0.7)2Zr2O7 exhibited pure fluorite phase. The thermal expansion coefficient (TEC) of Nd2Zr2O7 was significantly enhanced by 10 mol% Sc2O3 doping, but higher Sc2O3 doping decreased the TEC. The reduced crystal energy due to the presence of Sc3+ interstitial ions could cause the initial increase in the TEC, and the formation of fluorite phase might contribute to the reduced TEC. Considering the alleviation of the thermal expansion mismatch stress for the high-temperature applications of Nd2Zr2O7, Sc2O3 was an excellent dopant and there existed an optimal Sc2O3 content for the optimization design of compound compositions.

Enhanced thermal expansion and fracture toughness of Sc2O3-doped Gd2Zr2O7 ceramics

(Gd1−xScx)2Zr2O7 (x=0, 0.025, 0.05, 0.075, 0.1, 0.2) ceramics were synthesized by chemical co-precipitation and calcination and their phase structure, thermal expansion behavior and mechanical properties were investigated. (Gd1−xScx)2Zr2O7 (x=0, 0.025, 0.05, 0.075) exhibited pyrochlore structure. The ordering degree decreased and the lattice parameter increased with increasing the Sc2O3 content, but high Sc2O3 doping led to a pyrochlore-fluorite phase transformation and to a decrease in the lattice parameter. Among the (Gd1−xScx)2Zr2O7 ceramics investigated, (Gd0.925Sc0.075)2Zr2O7 yielded the largest thermal expansion coefficient (TEC). The structural disorder and lattice expansion could cause the initial increase in the TEC, and the decrease in the lattice parameter might contribute to the reduced TEC. Increasing Sc2O3 content benefited the fracture toughness of (Gd1−xScx)2Zr2O7, which could be attributed to the increased cohesive energy due to the lattice distortion and structural disorder.

Effects of scandium doping concentration on the properties of strontium cobalt oxide membranes

Perovskite-type mixed conducting oxides of SrCo1-yScyO3-δ (y=0.02-0.7) were synthesized by a combined EDTA-citrate complexing method. Different scandium doping concentrations in SrCo1-yScyO3-δ have significant effects on the phase structure, electrical conductivity, surface properties and oxygen permeation behaviour of the resultant membranes. SrCoO3-δ without scandium incorporation displayed a 2H BaNiO3-type structure with almost zero oxygen flux at high temperatures. Small amounts of Sc2O3 doping (y 0.1) were found to lower the membrane oxygen fluxes, with y³≥0.4 doped SrCo1-yScyO3-δ ceramics no longer showing any oxygen permeation.

Fluorescence emission enhancement of transparent Nd:YSAG ceramics by Sc2O3 doping

Up to 40% substitution of scandium for aluminum in YAG ceramics has been achieved, and the transparent Nd-doped Y3ScxAl(5−x)O12(Nd:YSAG) ceramics were successfully fabricated by sintering nanosized powder compacts under H2 atmosphere. It was found that 40% scandium substitution for aluminum can significantly enhance the light-emission intensity around 1064 nm of the Nd:YSAG ceramics by 2-3 times as compared with Nd:YAG single crystal without Sc2O3 doping when pumped with the same 808 nm diode laser. In addition, the material was found to have prolonged fluorescence lifetime.

Catalytic Performance of Metal Nanoparticles Supported by Ceramic Composite Produced by Partial Reduction of Solid Solution with Dopant

A composite with well-dispersed metal nanoparticles at a ceramic surface was produced by partial reduction of solid solution. It was found that a small amount of dopant, such as Al2O3, Cr2O3, or Sc2O3, accelerated the precipitation of the metal nanoparticles during the reduction. Catalytic performance of the composite for methanol reforming was evaluated. In the Ni-based catalysts, the dopant decreased the CO production by promoting a methanation reaction, while in the Co-based catalysts, the dopant did it by inducing a water–gas shift reaction. Co/MgO with Sc2O3 doping showed the most preferable reforming performance, high H2 production, and CO2 selectivity.

Self-frequency doubling in Nd,Sc_2O_3:LiNbO_3 at room temperature

Self-frequency doubling is reported in a Nd,Sc(2)O(3):LiNbO(3) single crystal. The Sc(2)O(3) doping produced room-temperature (20 degrees C) 90 degrees noncritical phase matching (theta = 90 degrees C). Under quasi-cw conditions, 0.14 mW of frequency-doubled 546-nm radiation was produced. The pump-to-green-light conversion efficiency was 11%/W with a 25-mW absorbed input power lasing threshold. Only the fundamental 1092-nm s-polarized oscillation was produced, rather than the p-polarized output, as reported for Nd,MgO:LiNbO(3). This simplified the cavity by elimination of the Brewster window needed to force the s-polarized output required for type I phase matching.