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MnO2 and CeO2 were doped to improve the corrosion resistance of CSZ (calcia-stabilized zirconia), and we studied the phase formation, mechanical properties, and corrosion resistance by molten mold flux. The volume fraction of the monoclinic phase gradually decreased as the amount of MnO2 doping increased. The splitting phenomenon of the t(101) peak was observed in 2Mn_CSZ, and in 4Mn_CSZ, it was completely split, forming a cubic phase. The relative density increased and the monoclinic phase decreased as the doping amount increased, leading to an increase in Vickers hardness and flexural strength. However, in 3Mn_CSZ and 4Mn_CSZ, where cubic phase formation occurred, the tetragonal phase decreased, leading to a reduction in these properties. MnO2-doped CSZ exhibited a larger fraction of the monoclinic phase compared to the original CSZ after the corrosion test, indicating worsened corrosion resistance. These results are attributed to the predominant presence of Mn3+ and Mn2+ forms, rather than the Mn4+ form, which has a smaller basicity difference with SiO2, and due to the low melting point. The monoclinic phase fraction decreased as the doping amount of CeO2 increased in CeO2-doped CSZ, but the rate of decrease was lower compared to MnO2-doped CSZ. The monoclinic phase decreased as the doping amount increased, but the Vickers hardness and flexural strength showed a decreasing trend due to the low relative density. The destabilization behavior of Ca in SEM-EDS images before and after corrosion was difficult to identify due to the presence of Ca in the slag, and the destabilization behavior of Ce due to slag after corrosion was not observed. In the XRD data of the specimen surface after the corrosion test, the fraction of the monoclinic phase increased compared to before the test but showed a lower monoclinic phase fraction compared to CSZ. It is believed that CeO2 has superior corrosion resistance compared to CaO because Ce predominantly exists in the form of Ce4+, which has a smaller difference in basicity within the zirconia lattice. [ABSTRACT FROM AUTHOR]

Lu2O3 and Y2O3 doping of 8, 11, and 18 mol% in ZrO2 were prepared by solid solution reaction, aiming to study the phase stabilization of Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2 in terms of phase formation and lattice distortion. The Rietveld refinement results indicated that Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2 followed the same trend in terms of cubic phase fraction, increasing from 25%–30% (8 mol%) to 95%–100% (11 and 18 mol%). This phase formation was confirmed by observing the same diffraction ring pattern observed for the Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2. The Vickers hardness of the Lu2O3‐doped ZrO2 was 4.3% higher than that of Y2O3‐doped ZrO2 at 8 mol%, but 9.7% and 14.8% lower at 11 and 18 mol%, respectively. This was likely caused by the lattice distortion effect of Y2O3 doping overpowering the field strength difference between Lu3+ and Y3+. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of the enhancement in the ionic conductivity resulting from cubic phase stabilization in MgO partially stabilized zirconia (MgPSZ) by Mn doping was studied by examining the local Zr‐O structure. Cubic phase (14 vol%) in MgPSZ was increased with the addition of MnO2, and 10 mol% Mn‐doped MgPSZ exhibited the highest cubic phase fraction (98.72%), which was analyzed by Rietveld refinement. In addition, only the cubic phase, not the monoclinic and tetragonal phases, was observed in the TEM‐SAED pattern of 10 mol% Mn‐doped MgPSZ. Doped Mn exhibited a high Mn2+/Mn4+ ratio, which was identified by X‐ray photoelectron spectroscopy (XPS). In addition, it indicates that oxygen vacancy formation by substitution of Mn2+ in the Zr4+ site in MgPSZ increased cubic phase fraction. Ionic conductivity of MgPSZ was improved by the cubic phase increase attributed to Mn doping, and 10 mol% Mn‐doped MgPSZ exhibited higher ionic conductivity than MgPSZ. To investigate the mechanism of the ionic conductivity improvement, Zr‐O local structure in Mn‐doped MgPSZ was analyzed by Zr K‐edge EXAFS of MgPSZ, and the number of bonding of the Zr‐O first shell decreased with increased Mn substitution. Therefore, it was considered that the oxygen vacancy generation led to an increase in the cubic phase and the number of ionic conduction sites. [ABSTRACT FROM AUTHOR]

The thermal expansion and ionic conduction of 15 mol% CaO-stabilized zirconia ( CSZ) with added Al2O3 were investigated. Specimens with 0.5 and 1 mol% Al2O3 maintained the cubic phase, and the thermal diffusivity increased from 0.499 to 0.661 mm2/s with a 1 mol% addition. The addition of 5 mol% caused a decrease in the thermal diffusivity (0.609 mm2/s) with the formation of the monoclinic phase. The thermal expansion coefficient of the CSZ decreased, and the thermal diffusivity increased with the addition of Al2O3. The ionic conductivity was increased up to the addition of 1 mol% due to scavenging of siliceous by Al2O3, while the 5 mol% addition showed a decrease in conductivity with the formation of the intergranular phase. [ABSTRACT FROM AUTHOR]

The electrical properties of 9 mol% MgO–ZrO2 (Mg-PSZ) with 1 mol% Al2O3 and the mechanisms for electrical degradation were investigated using structural, morphological, and electrochemical analyses. The addition of Al2O3 caused an increase in both the monoclinic and the Mg-rich phases at the grain boundaries in the Mg-PSZ. Coarse grains larger than 20 μm and an intergranular layer composed of the Mg-rich phase were identified in a specimen sintered at 1600 °C. This specimen exhibited a minimum of ionic conductivity (4.98 × 10−4 S cm−1 at 700 °C) due to the grain boundary resistance (245 Ω cm2), which dominated the overall resistance. A similar trend was observed over the entire temperature range (600–1500 °C). An intergranular siliceous impurity (SiO2) was present in conjunction with the Mg-rich phase. This impurity and the Mg-rich phase acted as a barrier layer for oxygen ion diffusion. The presence of the intergranular phases (i.e. the monoclinic and Mg-rich phases) contributed to the degradation of the ionic conductivity in Mg-PSZ with an Al2O3 addition. [ABSTRACT FROM AUTHOR]

The characteristics of Lu 2 O 3 -doped ZrO 2 as a solid electrolyte material were investigated in terms of its oxygen ion conductivity and flexural strength to realize its electrolytic function at intermediate and high temperatures. The effect of doping Lu3+, which has a high nuclear charge electric field strength, was examined through impedance spectroscopy, open-circuit potential measurements, and bending tests. The results with Lu 2 O 3 dopant were compared with those obtained with a widely used dopant, Y3+, having a similar ionic radius with Lu3+, as well as a dopant that provides high ionic conduction, Sc3+, having a smaller ionic radius with Zr4+. The results revealed that, at the same dopant concentration, both the ionic conductivity and the flexural strength of Lu 2 O 3 -doped ZrO 2 are higher than those of the widely used Y 2 O 3 -doped ZrO 2. The conductivity of 8 mol% Lu 2 O 3 -doped ZrO 2 surpassed that of 8 mol% Sc 2 O 3 -doped ZrO 2 in the range of 800–950 °C (0.153 S/cm vs. 0.121 S/cm at 900 °C). These results indicate the potential of Lu3+ as a dopant for enhancing the performance of ZrO 2 solid electrolytes. [ABSTRACT FROM AUTHOR]

Lu2O3 and Y2O3 doping of 8, 11, and 18 mol% in ZrO2 were prepared by solid solution reaction, aiming to study the phase stabilization of Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2 in terms of phase formation and lattice distortion. The Rietveld refinement results indicated that Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2 followed the same trend in terms of cubic phase fraction, increasing from 25%–30% (8 mol%) to 95%–100% (11 and 18 mol%). This phase formation was confirmed by observing the same diffraction ring pattern observed for the Lu2O3‐doped ZrO2 and Y2O3‐doped ZrO2. The Vickers hardness of the Lu2O3‐doped ZrO2 was 4.3% higher than that of Y2O3‐doped ZrO2 at 8 mol%, but 9.7% and 14.8% lower at 11 and 18 mol%, respectively. This was likely caused by the lattice distortion effect of Y2O3 doping overpowering the field strength difference between Lu3+ and Y3+. [ABSTRACT FROM AUTHOR]

The performance of zirconia nanoparticles (ZrO 2 NPs) is critically dependent on their dispersion and stability. Effective control of NP dispersion is crucial for achieving a high refractive index, transparency, and exceptional mechanical properties in organic-inorganic hybrid films that incorporate ZrO 2 NPs. In this study, we compared the crystalline properties and stability of ZrO 2 NPs synthesized via two distinct methodologies: solvothermal synthesis using a zirconium isopropoxide isopropanol complex (ZII, Zr(OCH(CH 3) 2) 4 ·(CH 3) 2 CHOH) and sol-gel synthesis using zirconyl chloride octahydrate (ZC, ZrOCl 2 ·8H 2 O). Both solutions exhibited precipitation, and the particles showed aggregation behavior. Despite being in a suspended state, the particles synthesized using the ZII precursor (T-ZrO 2) exhibited hard-sphere behavior, distinct interparticle boundaries, and a tetragonal crystalline phase. However, the particles produced using the ZC precursor (A-ZrO 2) were nearly amorphous without well-defined sizes and morphologies. Further, the hydroxyl end groups of both particle types were exchanged using a silane coupling agent (3-(trimethoxysilyl)propyl methacrylate, TMSPM) via hydrolysis and condensation reactions. The presence of the TMSPM groups on the surface of ZrO 2 NPs afforded surface-modified TMSPM-T-ZrO 2 with enhanced stability and prevented particle aggregation, thus maintaining the dispersion stability for up to one year under ambient conditions. The low surface energy and stabilization of the TMSPM-T-ZrO 2 NPs were influenced by the tetragonal crystalline phase, which was conducive to surface modification using a silane coupling agent. [Display omitted] • Synthesized TMSPM-T-ZrO 2 colloidal dispersion remains stable for up to one year. • The properties and stability of ZrO 2 NPs are influenced by their crystalline phases. • The tetragonal phase of ZrO 2 NPs has a lower surface energy compared to that of amorphous. [ABSTRACT FROM AUTHOR]

Improved dispersibility of zirconia nanoparticles (ZrO 2 NPs) is crucial in many optical applications, but traditional dispersion methods using dispersants or devices can be problematic. In this study, we propose a simple and novel dispersion method that controls the crystalline phase through yttrium (Y3+) doping to improve dispersibility. The ZrO 2 NPs colloidal sol was developed using three precursors – acetate-based zirconia (A-ZrO 2), acetate-based 3-yttria stabilized zirconia (A-3YSZ), and chloride-based 3-yttria stabilized zirconia (C-3YSZ). The A-3YSZ exhibited the most superior dispersibility among the samples due to its low surface energy. Furthermore, it maintained dispersibility even though precursor concentration increased up to 6 wt%. Our results show that A-3YSZ is an effective inorganic filler for improving the refractive index of an acrylate-based coating solution. This is due to its excellent dispersibility and simple synthesis without requiring additional chemical modification and complicated dispersion processes. [Display omitted] • Dispersibility control via the crystalline phase of YSZ. • Dispersibility was related to surface energy according to the crystalline phase. • Simple and novel method to prepare dispersed YSZ sol. • Equivalent to commercial grade. • Concentration of A-3YSZ improved up to 6 wt%. [ABSTRACT FROM AUTHOR]

The oxygen ion conductivity of zirconia-based solid electrolytes doped with 8mol% Y2O3–ZrO2 (YSZ) and 9mol% MgO–ZrO2 (Mg-PSZ) at high temperature was investigated in terms of their thermal behavior and structural changes. At room temperature, YSZ showed a single phase with a fluorite cubic structure, whereas Mg-PSZ had a mixture of cubic, tetragonal and some monoclinic phases. YSZ exhibited higher ionic conductivity than Mg-PSZ at temperatures from 600°C to 1250°C because of the existence of the single cubic structure and low activation energy. A considerable increase in the conductivity with increasing temperature was observed in Mg-PSZ, which showed higher ionic conductivity than YSZ within the higher temperature range of 1300–1500°C. A monoclinic-to-tetragonal phase transformation was found in Mg-PSZ and the lattice parameter of the cubic phase increased at 1200°C. The phase transformation and the large lattice free volume contributed to the significant enhancement of the ionic conductivity of Mg-PSZ at high temperatures. [ABSTRACT FROM AUTHOR]