Nb Substitution Research Articles

Enhanced Ferroelectric and Dielectric Properties of Niobium-Doped Lead-Free Piezoceramics.

Lead-free ceramics are promising candidates for replacing lead-based piezoelectric materials such as lead-zirconate-titanate (PZT) if they can compete in dielectric and ferroelectric characteristics. In this work, for lead-free piezoelectric ceramic, 0.74(Bi0.5Na0.5TiO3)-0.26(SrTiO3) (BNT-ST26) and niobium-substituted (Nb-BNT-ST26) ceramics were synthesized by solid-state reactions. The evolution of niobium substitution to the perovskite phase structure of BNT-ST26 ceramics was confirmed by X-ray diffraction (XRD) analysis and Raman spectra. Electromechanical properties of Nb-BNT-ST26 ceramics initially increased with the addition of niobium up to 0.5% and decreased with a further increase in Nb content. Temperature-dependent dielectric curves showed that the depolarization temperature (Td) decreased below room temperature because of Nb substitution. The composition with 0.5% Nb yielded a maximum bipolar strain (Smax) of 0.265% and normalized strain of d33* ~ 576 pm/V under an electric field of 4.6 kV/mm at room temperature. At this critical concentration of 0.5% Nb, maximum saturation polarization of 26 μC/cm2 was achieved. The dielectric constant with temperature peaks became more diffused and the depolarization temperature decreased with the increasing Nb content. The study concludes that Nb-doped BNT-ST26 is an excellent material for high-temperature, stable, frequency-dependent, lead-free piezoelectric devices.

Complex defect chemistry of hydrothermally-synthesized Nb-substituted β′-LiVOPO4

Nb substitution via hydrothermal synthesis led to a new β′-LiVOPO4 phase with complex defect chemistries. The samples showed improved high-voltage rate capabilities and an enlarged voltage hysteresis due to a partial V4+/V3+ redox reaction.

The effect of systematic substitution of Nb with Ti on a potential high-temperature shape memory alloy: B2 NbRu

NbRu has been considered as a potential high-temperature shape memory alloy due to its high martensitic transformation temperature, however, it has poor superelasticity and other shape memory properties, which limits its applications. In this paper, the effect of systematic substitution of Nb with Ti on the structural, thermodynamic, and elastic properties of supercell 2x2x2 B2 Ru50Nb50-xTix spanning the entire composition range (x = 0, 6.25, 12.50, 18.75, 25.00, 31.25, 37.50, 43.75, 50 at. %) is investigated using ab initio calculations. Elasticity results showed that the mechanical stability of the B2 phase improved with increasing Ti content, which could be associated with a decrease in transformation temperature. However, a suitable composition range within which Cʹ~0, resembling that of well-known TiNi, is identified. This predicts Ti addition to be effective in improving shape memory properties of B2 NbRu alloy.

Activation energy study on nanostructured niobium substituted Mg2Ni intermetallic alloy for hydrogen storage application

The magnesium-based metallic alloys have been exhibited to be the improved hydrogen storage materials. In the present investigation, a nanostructured Mg67Ni33 and Niobium substituted intermetallic compound was prepared by a high-energy ball milling technique for hydrogen storage application. Niobium substitution on the pure crystalline intermetallic compound changed the structure of the crystalline to semi-amorphous as well as changed the interplanar spacing after 30 h of milling. Furthermore, the effect of Nb substitution on the inter-planar shift and its corresponding implications on lattice strain, crystallite size, and unit cell volume of the Mg2Ni compound were also discussed. Transmission electron microscope studies confirm the particle size was reduced to less than 100 nm for 30 h of milling. However, SEM images confirm the agglomeration of these nanoparticles and form spherical particles of size around 3–5 μm. XRD and EDS authenticate the presence of oxides. Kissinger’s analysis confirmed that Mg2Ni powder exhibited lower activation energy of 64.101 kJ mol−1 than niobium-substituted alloy powders. The hydrogen charge and discharge potential of these compounds are discussed in detail.

Cerium(III) Niobate Layered Perovskites: Abnormal Optical Absorption Modulations by Tuning of B-Site Composition and Perovskite Layer Charge Control.

The cerium-introduced layered perovskite of RbCeTa2O7 has exhibited a specific optical absorption due to metal-to-metal charge transfer transitions between Ce 4f and transition metal d-orbitals to show the unique pale-green coloration, which is different from conventional coloration mechanisms. To further extend the coloring state based on the same mechanism, in this work, a series of the [Ce(Ta,Nb)2O7]- layered perovskites, Rb1-xCsx[Ce(Ta1-xNbx)2O7] (x = 0∼1), with Nb substitutions in the perovskite units have been prepared and investigated in terms of those crystal structures and optical absorption mechanism. The Rietveld analysis using the XRD profile and EXAFS analyses well refined those structures as the Dion-Jacobson-type layered perovskite. The color of solid solutions gradually changed from pale-green to dark reddish-brown with increasing amount of substituted niobium. The unique coloring state change behavior of solid solutions from pale-green to dark reddish-brown depending on the amount of the substituted niobium is not observed in the other layered perovskite analogues (e.g., La and Pr analogues). The first-principles calculation based on the density functional theory method indicated that the band structural change should be a key factor for the coloration modulation. Furthermore, the redox ability through the charge modulation of the perovskite layer, which is a specific function of the cerium-based layered perovskite, was also investigated for the niobate [CeNb2O7]- perovskite layer, resulting in the anisotropic lattice changes similar to those of a Ta analogue with different structural changes in the stacking and in-plane directions. The accompanying change in electronic structure led to a clear modulation in optical absorption, yielding a drastic change in the coloring state from dark brown to yellow.

High critical field superconductivity at ambient pressure in MoB2 stabilized in the P6/mmm structure via Nb substitution

Recently it was discovered that, under elevated pressures, MoB$_2$ exhibits superconductivity at a critical temperature, $T_c$, as high as 32 K. The superconductivity appears to develop following a pressure-induced structural transition from the ambient pressure R$\bar{3}$m structure to an MgB$_2$-like P6/mmm structure. This suggests that remarkably high $T_c$ values among diborides are not restricted to MgB$_2$ as previously appeared to be the case, and that similarly high $T_c$ values may occur in other diborides if they can be coerced into the MgB$_2$ structure. In this paper, we show that density functional theory calculations indicate that phonon free energy stabilizes the P6/mmm structure over the R$\bar{3}$m at high temperatures across the Nb$_{1-x}$Mo$_x$B$_2$ series. X-ray diffraction confirms that the synthesized Nb-substituted MoB$_2$ adopts the MgB$_2$ crystal structure. High magnetic field electrical resistivity measurements and specific heat measurements demonstrate that Nb$_{1-x}$Mo$_x$B$_2$ exhibits superconductivity with $T_c$ as high as 8 K and critical fields approaching 6 T.

Effect of Nb substitution on the electronic property of lead-free piezoelectric (Na0.41K0.09Bi0.50)TiO3 single crystal: Optical absorption and photoelectron study

Single crystals of undoped and Nb doped sodium and potassium-bismuth titanate at the morphotropic phase boundary (MPB) composition [(Na0.41K0.09Bi0.50)TiO3: NKBT] were grown from high temperature solutions. The effect of Nb doping on the electronic property of NKBT was investigated by optical transmission and photoelectron spectroscopy (PES). The optical absorption shows that the bandgap having the lowest energy is indirect in nature and increases with the increase in the Nb concentration in the lattice. The estimated Urbach energy increases with the increase of Nb concentration signifying an increase in the disorder in the lattice on Nb doping. The PES revealed that the valence band maxima (VBM) exhibit red shift on Nb doping. It also revealed the presence of in-gap states probably due to Ti3+ defect and oxygen vacancy. Moreover, inline with the optical measurement, the PES showed that there is a decrease in the energy gap between the VBM and defect state with the Nb doping. Furthermore, the angle resolved PES measurement confirmed the presence of both the direct and indirect bandgaps in the crystal.

Fermiology and Origin of T_{c} Enhancement in a Kagome Superconductor Cs(V_{1-x}Nb_{x})_{3}Sb_{5}.

Kagome metals AV_{3}Sb_{5} (A=K, Rb, and Cs) exhibit a characteristic superconducting ground state coexisting with a charge density wave (CDW), whereas the mechanisms of the superconductivity and CDW have yet to be clarified. Here we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of Cs(V_{1-x}Nb_{x})_{3}Sb_{5} as a function of Nb content x, where isovalent Nb substitution causes an enhancement of superconducting transition temperature (T_{c}) and the reduction of CDW temperature (T_{CDW}). We found that the Nb substitution shifts the Sb-derived electron band at the Γ point downward and simultaneously moves the V-derived band around the M point upward to lift up the saddle point (SP) away from the Fermi level, leading to the reduction of the CDW-gap magnitude and T_{CDW}. This indicates a primary role of the SP density of states to stabilize the CDW. The present result also suggests that the enhancement of superconductivity by Nb substitution is caused by the cooperation between the expansion of the Sb-derived electron pocket and the recovery of the V-derived density of states at the Fermi level.

Terahertz Faraday Rotation of SrFe12O19 Hexaferrites Enhanced by Nb Doping.

The magneto-optical and dielectric behavior of M-type hexaferrites as permanent magnets in the THz band is essential for potential applications like microwave absorbers and antennas, while are rarely reported in recent years. In this work, single-phase SrFe12–xNbxO19 hexaferrite ceramics were prepared by the conventional solid-state sintering method. Temperature dependence of dielectric parameters was investigated here to determine the relationship between dielectric response and magnetic phase transition. The saturated magnetization increases by nearly 12%, while the coercive field decreases by 30% in the x = 0.03 composition compared to that of the x = 0.00 sample. Besides, the Nb substitution improves the magneto-optical behavior in the THz band by comparing the Faraday rotation parameter from 0.75 (x = 0.00) to 1.30 (x = 0.03). The changes in the magnetic properties are explained by a composition-driven increase of the net magnetic moment and enhanced ferromagnetic exchange coupling. The substitution of the donor dopant Nb on the Fe site is a feasible way to obtain multifunctional M-type hexaferrites as preferred candidates for permanent magnets, sensors, and other electronic devices.

Processing and properties of PSZT 95/5 ceramics with varying Ti and Nb substitution

AbstractNiobium doped lead‐tin‐zirconate‐titanate ceramics near the PZT 95/5 orthorhombic AFE – rhombohedral FE morphotropic phase boundary Pb1‐0.5y(Zr0.865‐xTixSn0.135)1‐yNbyO3 were prepared according to a 22+1 factorial design with x = 0.05, 0.07 and y = 0.0155, 0.0195. The ceramics were prepared by a traditional solid‐state synthesis route and sintered to near full density at 1250°C for 6 h. All compositions were ∼98% dense with no detectable secondary phases by X‐ray diffraction. The ceramics exhibited equiaxed grains with intergranular porosity, and grain size was ∼5 µm, decreasing with niobium substitution. Compositions exhibited remnant polarization values of ∼32 µC/cm2, increasing with Ti substitution. Depolarization by the hydrostatic pressure induced FE‐AFE phase transition was drastically affected by variation of the Ti and Nb substitution, increasing at a rate of 113 MPa /1% Ti and 21 MPa/1% Nb. Total depolarization output was insensitive to the change in Ti and Nb substitution, ∼32.8 µC/cm2 for the PSZT ceramics. The R3c‐R3m and R3m‐Pm3m phase transition temperatures on heating ranged from 90 to 105°C and 183 to 191°C, respectively. Ti substitution stabilized the R3c and R3m phases to higher temperatures, while Nb substitution stabilized the Pm3m phase to lower temperatures. Thermal hysteresis of the phase transitions was also observed in the ceramics, with transition temperature on cooling being as much as 10°C lower.

Improvement of hydrogenation sorption properties of Ti0.90V0.30Mn1.00Ni0.80 for ultra-high pressure metal-hydride compressor

Metal-hydride compressors are considered as an alternative to mechanical compressors in Hydrogen Refueling Stations. In this paper, several Ti-based AB2 compounds were synthesized and their hydrogen sorption properties were evaluated under ultra-high pressure up to 40 MPa. All the studied compounds exhibit absorption plateau pressure close to or higher than 10 MPa at 30 °C. The substitution by a small amount of Al was shown to drastically decrease the hysteresis. All the compounds herein studied follow the trend ln(P)∝−V0, except for the Nb-containing compound. This compound has a different behavior towards hydrogenation and exhibits sorption pressure much higher than expected from the above-mentioned relationship. It was confirmed that the Al and Nb substitution in AB2 compounds plays a great role on reducing hysteresis and increasing the sorption pressure, respectively.

Influence of equiatomic Zr/(Ti,Nb) substitution on microstructure and ultra-high strength of (Ti,Zr,Nb)C medium-entropy ceramics at 1900 °C

High-temperature mechanical properties of medium-entropy carbide ceramics have attracted significant attention. Tailoring the microstructure is an effective way to improve these high-temperature mechanical properties, which can be affected by the evolution of the enthalpy and entropy, as well as by lattice distortion and sluggish diffusion. In this study, the effects of equiatomic Zr/(Ti,Nb) substitution (Zr content of 10–40 at%) on the microstructure and high-temperature strength of (Ti,Zr,Nb)C medium-entropy ceramics were investigated. The grain size of the (Ti,Zr,Nb)C medium-entropy ceramics was refined from 9.4±3.7 to 1.1±0.4 μm with an increase in the Zr content from 10.0 to 33.3 at%. A further increase in the Zr content to 40 at% resulted in a slight increase in the grain size. At 1900 °C, the (Ti,Zr,Nb)C medium-entropy ceramics with the Zr contents of 33.3 and 40 at% exhibited ultra-high flexural strengths of 875±43 and 843±71 MPa, respectively, which were higher than those of the transition metal carbides previously reported under similar conditions. Furthermore, relatively smooth grain boundaries, which were detected at a test temperature of 1000 °C, transformed into curved and serrated boundaries as the temperature increased to 1900 °C, which may be considered the primary reason for the improved high-temperature flexural strength. The associated mechanism was analyzed and discussed in detail.

Narrow bandgap potassium titanate-molybdate-based d ferroelectrics

The bulk photovoltaic effect observed in ferroelectric materials can enable photovoltaic performance beyond the Shockley–Queisser limit of efficiency. This requires the use of ferroelectrics with strong polarization and low bandgap (Eg) that are typically contradictory in the common perovskite oxides ferroelectrics. Here, we use first-principles calculations to study the KNbO3–K(Ti0.5Mo0.5)O3 (KNTM) solid solutions as possible narrow-gap ferroelectric materials. KTM, the end-member of the recently discovered KNTM solid solution system, maintains a ferroelectric polarization similar to that of other K-based systems due to its d0 configuration at the B-site. The substitution of Nb in KTM reduces Eg from 2.9 of KTM to 1.83 eV for an unstrained system and 1.7 eV for a compressively strained system, while maintaining ferroelectricity. The combination of narrow Eg, strong ferroelectricity, low toxicity, and abundance of the constituent elements make Nb-substituted KTM a promising candidate material for photoferroelectric applications.

Enhanced relaxor behavior and high energy storage efficiency in niobium substituted (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics

The microstructure, dielectric properties, relaxor behavior, and energy storage efficiency of un-substituted and niobium (Nb) substituted (Ba0.85 Ca0.15)(Zr0.1 Ti0.9) 1-x NbxO3 (for x = 0, 0.02 and 0.05) samples prepared by the solid-state reaction method has been studied in detail. All the samples exhibited perovskite structure with no trace of impurity. Composition-dependent phase transition was also observed on the addition of Niobium. At room temperature, the co-existence of rhombohedral and tetragonal phases is observed in the unsubstituted samples. As the composition changes from x = 0.02 to x = 0.05, a structural change from tetragonal to cubic is observed. A remarkable reduction in grain size, from 90 μm (for x = 0) to 1.21 μm for (x = 0.05), is observed with the addition of Niobium. This result suggests that Niobium acts as a grain growth inhibiter in barium calcium zirconium titanate (BCZT) ceramics. The effect of Niobium on transition temperature is studied from the temperature-dependent dielectric permittivity graph. It was clear that the transition temperature shifted to a lower temperature region, and for x = 0.05, at a very low temperature (−23 °C/250 K) the tetragonal to cubic transition was observed. At x = 0.05, the temperature-dependent dielectric permittivity showed a broadened curve, indicating a diffuse phase transition. The diffuse phase transition in Nb substituted samples is explained by Uchino and Nomura modified Curie Weiss law.Moreover, the observations on temperature-dependent dielectric permittivity measurements at various frequencies suggest that the substitution of Nb5+ induces relaxor behavior. The energy storage efficiency of unsubstituted and Nb substituted samples was calculated from the polarization versus electric field graph. A high storage efficiency of 84% was obtained for the Nb substituted sample (x = 0.05) at 12 kV cm−1. Enhanced relaxor behavior and increased storage efficiency were observed in (Ba0.85 Ca0.15)(Zr0.1 Ti0.9) 1-x NbxO3 at x = 0.05. Thus we suggest that these are promising materials for energy storage applications.

Solution epitaxy of single-crystal and single-domain KNbO3 film with a great photovoltaic current

As a classic ferroelectric material, orthorhombic perovskite KNbO3 demonstrates a large electro-optical coefficient, high refractive index, and excellent nonlinear optical property. These make single-crystal KNbO3 films being long-pursued for lead-free sensor or optoelectronic device applications. However, it remains a challenge to obtain high-quality single-crystal KNbO3 films because of the volatility of potassium at a high growth temperature. In this work, single-crystal KNbO3 films with a tunable thickness have been successfully fabricated by a low-temperature (∼220 °C) hydrothermal epitaxy on cubic single-crystal Nb:SrTiO3 substrates. Interestingly, the KNbO3 film was investigated to adopt a single-domain structure with a polarization direction pointing to the substrate. In-depth characterization reveals an intriguing disordered region of approximately 0.6–1.2 nm because of partial Nb substitution of Ti near the interface, giving rise to the coexistence of Ti3+ and Ti4+ ions. Such region is proposed to release a large interface strain energy from a large lattice misfit (∼2.3%) between {011}KNbO3 and {100}Nb:SrTiO3 and reduce interfacial electrostatic energy via screening of the positive polar surface of KNbO3. This allows to drive a hydrothermal epitaxy of single-crystal and single-domain KNbO3 without forming a typical dislocation. The films demonstrate a great photovoltaic short-circuit current of 15.65 μA/cm2 under the 375 nm laser irradiation of 500 mW/cm2 light intensity, and the corresponding photoresponsivity is the highest among the emerged KNbO3-based materials. Such improvement in the photoresponsivity has been attributed to a successful low-temperature solution epitaxy of single-crystal and single-domain KNbO3 films, where K deficiency can be significantly suppressed. These findings suggest that a solution epitaxy strategy is effective in producing high-quality ferroelectric films for lead-free optoelectronic or self-powered photodetector device applications.

Niobium speciation in minerals revealed byL2,3-edges XANES spectroscopy

AbstractThe systematic mineralogy of niobium (Nb) is complex, with more than one hundred species dominated by multicomponent oxides of similar chemistry. The determination of Nb speciation in solids (i.e., the distribution between the phases and the crystal-chemical environment of Nb) is thus a challenge in geological contexts. Here, we present the first Nb L2,3-edges X-ray absorption near-edge structure (XANES) measurements on various Nb minerals and synthetic oxides with geological relevance. The interpretation of Nb L2,3-edges XANES spectra in the light of crystal-field theory shows the sensitivity of spectra to local site symmetry and electronic environment around Nb atoms. Crystal-field multiplet simulations give estimates of the 10Dq crystal-field parameter values for Nb5+, which range from 2.8 to 3.9 eV depending on Nb coordination and Nb—O distances. Rather than a 10Dq vs. R–5 relationship (where R represents the average Nb-O bond distance) expected in a point-charge model, we find a R–3 dependence with the crystal-field splitting for reference materials with octahedrally coordinated Nb. Complementary ligand-field multiplet simulations provide evidence of charge transfer between Nb and O. The contribution of the ionic and covalent characters to the Nb-O bonds is equivalent, unlike more ionic 3d metal–O bonds. This systematic characterization of the L2,3-edges XANES spectral properties of Nb provides information on the mechanisms by which Nb5+ substitutes for Fe3+, Ti4+, or Ce4+ in oxides common in geological contexts. Whereas the substitution of Nb5+ for Ce4+ does not modify the local structure of the cation site in cerianite, the substitution of Nb5+ for Ti4+ in rutile and anatase results in an increase of the cation-ligand distance and a decrease in the symmetry of the cation site. Conversely, the substitution of Nb5+ for Fe3+ in hematite and goethite results in a smaller cation site distortion. Our study demonstrates the usefulness of L2,3-edges XANES spectroscopy to determine Nb speciation in minerals to understand the processes of enrichment of this critical metal.

An experimental and density functional theory studies of Nb-doped BiVO4 photoanodes for enhanced solar water splitting

In this work, the influence of Nb doping on the photoelectrochemical (PEC) water splitting activity of monoclinic BiVO4 photoanode is explored using experimental and theoretical studies. A facile hydrothermal method is proposed for the synthesis of Nb-doped BiVO4 nanostructured thin films and detailed characterization was carried out to understand the morphology, crystal structure, optical, band edge, and electrochemical properties. The PEC studies revealed that the doping of Nb brings about a fourfold enhancement in BiVO4 photocurrent reaching ∼ 2.01 mA cm−2 at 1.23 V vs reference hydrogen electrode (RHE). The doping of Nb was found to increase the carrier density in the bulk of BiVO4 and improve the charge separation, charge transfer, diffusion, and decrease the charge transfer resistance at the BiVO4/electrolyte interface. Importantly, a charge separation efficiency of ∼ 98% was achieved (at 1.23 V vs RHE) with a photocurrent density of ∼ 4.5 mA cm−2 (with hole scavenger) and stoichiometric H2/O2 evolution (2:1) upon Nb doping. Furthermore, the density functional theory (DFT) calculations indicated changes in bandgap and density of states which agree with the experimental results indicating favorable transformation in the bulk and surface properties of BiVO4 after the Nb substitution.

Enhanced thermoelectric performance of n-type Nb-doped PbTe by compensating resonant level and inducing atomic disorder

The inferior thermoelectric performance of n-type PbTe limits the overall conversion efficiency in PbTe-based thermoelectric devices. Here, we introduce Sb and Cu2Te into n-type Nb-doped PbTe for achieving ultra-high thermoelectric performance. The co-doping of Sb and Cu effectively optimizes carrier concentration to compensate for the resonant level in Nb-doped PbTe alloys, and consequently achieves superior electrical performance over a wide temperature range. Meanwhile, by combining extended X-ray absorption fine structure and exhaustive electron microscopy investigations, we found Nb and Sb substitutions at Pb sites induce atomic disorders, such local mass fluctuation and local strain variation, in the lattice, and Cu2Te further results in microsized segregations and nanoprecipitates, which significantly suppress lattice thermal conductivity. Eventually, a peak ZT of ∼1.32 at 823 K and a high average ZTave ∼1.01 in the range from 323 to 823 K are achieved in the Pb0·975Nb0·02Sb0·005Te-0.004Cu2Te. Based on our findings, we innovatively employ comprehensive characterization to reveal the origin of ultrahigh thermoelectric performance in n-type Nb-doped PbTe within a wide temperature range, which should be generalized to other thermoelectric materials.

Microstructure and First Hydrogenation Properties of TiHfZrNb1-xV1+x Alloy for x = 0, 0.1, 0.2, 0.4, 0.6 and 1.

The effect of the substitution of Nb by V on the microstructure and hydrogen storage properties of TiHfZrNb1−xV1+x alloys (x = 0.1, 0.2, 0.4, 0.6 and 1) was investigated. For x = 0, the alloy was pure BCC and upon the substitution of niobium by vanadium, the BCC was progressively replaced by HCP and FCC phases. For x = 0.6, a C15 phase was also present and becomes the main phase for x = 1. The substitution greatly enhanced the first hydrogenation and makes it possible at room temperature under 20 bars of hydrogen. The capacity of all substituted alloys was around 2 wt.%.

Exploring the Compositional Space of High-Entropy Alloys for Cost-Effective High-Temperature Applications

High-entropy alloys (HEAs) are nearly equimolar multi-principal element alloys, exhibiting exceptional thermal and mechanical properties at extreme conditions such as high-temperatures and stresses. Since the first discovery and early conceptualization of conventional HEAs nearly two decades ago, HEAs with far-from-equimolar compositions have attracted substantial interest to provide a broader range of material properties and to adjust price fluctuations and availability of commodities. Here, we present a first-principles investigation of non-equimolar chromium-manganese-iron-cobalt-nickel (CrMnFeCoNi) HEAs and effects of molybdenum (Mo) and niobium (Nb) substitutions on cost, phase stability and solubility, and mechanical and thermal performance up to 1000 K operational temperature. Virtual-crystal approximation is used to expediently approximate random solid solutions at the disordered mean-field limit. Using multi-objective metaheuristics built on a first-principles database, golden compositions are predicted for thermally well-insulated components and effective heat sinks. Replacing Co with Fe lowers commodity costs without hindering phase stability and solubility. Lower Ni concentration leads to lower thermal conductivity, indicating better thermal insulation, while reducing Mn concentration significantly increases the thermal conductivity, indicating better performing heat sinks. Moving away from equimolar ratios commonly increases the thermal expansion coefficient, which could generate higher thermal stresses. Nb and Mo substitution always lead to substantially higher commodity cost and density but with an increment in the mechanical performance due to solid-solution hardening. However, alloying with Mo and Nb is the only compositional space that reduces the thermal conductivity and thermal expansion coefficient.