Multicomponent Solid Solutions Research Articles

The thermodynamics of multicomponent high-entropy materials

AbstractHuman development has been based for millennia on manufacturing materials using a conventional alloying strategy of selecting a principal component for the primary property requirement of the material and then adding one or two minor alloying components at relatively low concentrations, either to enhance the primary property or to provide additional secondary properties. We have discovered relatively recently that, with sufficiently large numbers of alloying elements added in sufficiently large concentrations, the configurational entropy of mixing can often become large enough to suppress the formation of brittle compound phases, leading instead to the formation of multicomponent high-entropy solid solutions. In fact, there are literally billions of multicomponent high-entropy single-phase solid-solution materials, with a wide range of exciting new properties, in most cases relatively straightforward to manufacture by conventional processing methods. There seems, however, to be an upper limit to these effects, so that, beyond about ten or twelve alloying components, the inevitable increase in chemical diversity prevents the configurational entropy of mixing from suppressing the increasingly strong chemical reactions between them. This paper discusses in more detail the thermodynamic balance between: (1) increasing configurational entropy and promoting high-entropy solid solutions; and (2) increasing chemical diversity and promoting the formation of brittle compound phases. This is discussed on the basis of regular solution thermodynamics, without the need for more complex, semi-empirical Calphad calculations that can sometimes obscure the underlying key physical and chemical principles. The results show: (1) why large single-phase solid-solution regions are relatively common in multicomponent phase space; (2) why single-phase solid solutions are often favoured over stoichiometric compounds for large numbers of chemically similar components, in concentrated rather than dilute proportions, at high temperatures, and after quenching to room temperature; and (3) the difficulty of detailed thermodynamic analysis in multicomponent materials because of the large numbers of thermodynamic parameters that need to be known and the corresponding lack of underlying thermodynamic measurements.

High Oxygen Reduction Efficiency and Durability of Nano-Honeycomb Pt3(NiFeCo) Replenished by High-Entropy Metallic Glass Support.

Developing low-Pt oxygen reduction reaction (ORR) catalysts with high efficiency and robustness is critical for practical fuel cells. The most advanced ORR catalysts either feature high percentages of Pt (>70 at.%) or exhibit poor durability when reducing Pt loading. Herein, a multicomponent solid-solution Pt3(FeCoNi) honeycomb nano-framework supported by the specially designed high-entropy metallic glass (MG) is reported for efficient ORR. This hybrid catalyst with a low surface Pt loading of 5.79µgcm-2 displays exceptional mass and specific activities of 7.02Amgpt -1 and 8.15mAcmPt -2 at 0.9V, respectively, which are ≈15 and 22 times higher compared with commercial Pt/C. The analyses reveal the weakened chemisorption of oxygenated species, which is induced by the strong strain and ligand effects originating from the synergistic multicomponent alloying. This in turn enhances the intrinsic ORR activity. Moreover, benefiting from a unique replenishment behavior, the hybrid catalyst delivers ultra-high durability with negligible activity decay even after 50 000 potential cycles. This mechanism is achieved by sacrificing the interior MG supplementary support to dynamically compensate for the loss of catalytically active surface. The work provides an alternative way to design more efficient and durable low-Pt electrocatalysts for electrochemical devices.

Synthesis and oxidation behavior of Ti-Zr-Ta(Hf) high entropy carbide nanopowders by sol-gel method

Multi-component solid solution carbide is a promising material due to its excellent mechanical strength, thermal stability, and resistance to chemical corrosion. In this study, we intentionally designed and synthesized three types of solid solution carbide powders using the sol-gel method: (Ti1/3Zr1/3Ta1/3)C, (Ti1/3Zr1/3Hf1/3)C and (Ti1/4Zr1/4Ta1/4Hf1/4)C. The results show that the liquid-phase precursor undergoes pyrolysis at 800 °C and subsequently form homogeneous single face-centered cubic structure solid solutions upon thermal treatment at temperatures exceeding 1800 °C. The obtained powders exhibited ultra-fine and uniform particle sizes of 340 nm, 248 nm, and 401 nm, respectively. Furthermore, the oxidation behavior of the three types of carbide powders in air shows that Hf and Ta elements are of great significance in improving oxidation resistance. The solid solution of Hf increases the initial oxidation temperature, while Ta tends to form a complex oxide with Zr, which helps to improve the oxidation temperature resistance. This work therefore contributes filling the gap of employing the sol-gel method in the fabrication of multi-component solid solution carbide materials and provides novel insights into their synthesis mechanism and oxidation behaviours.

Ablation resistance of (Hf⅓Zr⅓Ta⅓)C solid solution ceramic coating for carbon/carbon composites at 2100 °C

Multicomponent solid solution ceramics have attracted extensive attention for their superior ablation resistance and high-temperature resistance, which are expected to extend the service life of carbon/carbon (C/C) composites under an ablation environment above 2000 °C. Herein, we synthesized (Hf⅓Zr⅓Ta⅓)C solid solution ceramic powders via carbothermal reduction. Then a dense (Hf⅓Zr⅓Ta⅓)C solid solution ceramic coating was deposited on SiC-coated C/C composites by supersonic atmospheric plasma spraying. The coated samples exhibited a low linear ablation rate of −0.61 μm/s after ablation for 120 s, mainly associated with the formation of a compact oxide scale consisting of (Hf, Zr)6Ta2O17 and (Hf, Zr)O2. The refractory (Hf, Zr)O2 skeleton structure possessed good thermal endurance, and the Ta-rich oxide melt filled the defects of the skeleton.

Next-generation multicomponent SMAs: leveraging HEA empirical parameters

Empirical rule calculation, commonly used for phase selection of high entropy alloys (HEAs), provides valuable guidelines for designing multicomponent solid solutions. It is unknown whether the technique can offer a similar design strategy for multicomponent intermetallics that undergo B2−B19′ transformation. Establishing such guidelines can significantly accelerate the pace of discovery for new shape memory alloys (SMAs) by narrowing down the search area within the vast compositional design space of multicomponent alloys. In this study, we compiled hundreds of data on medium and high-entropy NiTi-based alloys exhibiting B2−B19′ transformation. Our objective was to construct a more comprehensive Ω−δ map and locate multicomponent SMAs on it. Additionally, we conducted a thorough analysis to establish a correlation between transformation temperatures and compositional features in medium and high-entropy SMAs (ME and HE-SMAs). This correlation can be leveraged to design SMAs with targeted transformation temperatures.

Local Nanostructure in Multicomponent High-Entropy Materials

Multicomponent phase space contains extended regions of random or near-random multicomponent solid-solution single phases, stabilised by a relatively large configurational entropy of mixing that can often (though not always) suppress compound formation between the different atomic species. The present paper shows that there are very extensive variations of local nanostructure, local atomic clusters and associated local lattice strains within multicomponent high-entropy solid-solution single phases such as the fcc Cantor alloys, bcc Senkov alloys and rock-salt-structured Rost mono-oxides, even when there is no short-range ordering, i.e. even when the solid solution is completely random or ideal. There are, for instance, many billions of different local nanostructures and different local atomic clusters in equiatomic five-component fully random solid-solution single-phase materials such as the original fcc Cantor alloy CrMnFeCoNi and the original bcc Senkov alloy VNbMoTaW, extending over distances of many microns, with associated fluctuating hydrostatic and shear lattice strains of several percent. The number and extent of the variations in local nanostructure, atomic clusters and lattice strains increase dramatically to even higher values with increasing number of components in the material. The present paper also shows that there are similar variations in local nanostructure, local atomic clusters and associated local lattice strains surrounding point defects such as vacancies, line defects such as dislocations and planar defects such as grain boundaries and external surfaces, influencing many important material properties such as diffusion, plastic flow, recrystallisation, grain growth and catalysis. The number and extent of the variations in local nanostructure, atomic clusters and lattice strains make it difficult to have too much confidence in structures and properties of multicomponent high-entropy materials calculated using ab initio and other atomistic computer modelling techniques, since these techniques are restricted to relatively small numbers of atoms and are unable to sample effectively the full range of local structures and properties.

CALPHAD, preparation, and mechanical properties of quaternary solid solution nitrides with various nitrogen stoichiometry

High-entropy ceramics have gained increasing interest due to unique properties unattainable by traditional materials. Though a large number of high-entropy ceramics have emerged, there was still in lack of theoretical predictions of phase composition on multicomponent solid solutions, which was probably caused by the composition complexity. In this work, employing Thermo-Calc and TCHEA4 database, a series of equilibrium phase data was generated from quaternary solid solution nitrides formed by the five elements of Ti, V, Cr, Zr, and N, while five quaternary solid solution nitrides with various nitrogen stoichiometry were prepared by SPS utilizing commercially available transition metal and their nitrides at 1600 °C. The detection of phase composition during the experiment and thermodynamic calculation confirmed that an increase in nitrogen content was beneficial for the formation of a single-phase solid solution. Due to the variation of nitrogen stoichiometry, the concentrations of nitrogen-metal bonds changed accordingly, resulting in different relative densities and mechanical properties. On the basis of the experimental data, CALPHAD, with a maximum absolute error of only 8.31 %, was established, providing a powerful tool for predicting phase in the complex composition-temperature space of compositionally complex ceramics.

Enhanced energy-storage performance with optimized thermally stable dielectric property in BNT–BST ceramics modified by KNN doping

Developing environmental-friendly materials with high-density energy storage is of paramount importance to meet the burgeoning demands for energy storage. In this study, we harness the modulation of a multicomponent solid solution by introducing KNN as a third element into the BNT–BST system, thereby achieving a marked enhancement in both energy storage performance and the temperature stability of the dielectric constant. BNBST–4KNN stands out for its exceptional dielectric stability, with a dielectric constant variation rate within 10% across a broad temperature range of [Formula: see text]C to [Formula: see text]C, a feat attributed to the flattening and broadening of the [Formula: see text] peak. BNBT–2KNN exhibits superior energy storage capabilities, with an energy storage density of 1.324 J/cm3 and an energy storage efficiency of 72.3%, a result of the P–E loop becoming more slender. These advancements are pivotal for the sustainable progression of energy storage technologies.

Concentration effects in multicomponent metallic solid solutions

In the equiatomic approximation, the dependence of the lattice FCC parameter and the Debye temperature from the atomic fate x of the doping element, which is alternately represented by all elements of a multicomponent solid solution, including high-entropy alloys were obtained. The calculations were carried out on the example of a five-component (based on Cu, Ni, Co, Fe, and Al) or six-component (based on Cu, Ni, Co, Fe, and Cr, Ti) metal systems. It was found that by varying x within x = (0 - 0.3), it is possible to obtain a change in the lattice FCC parameter from 0 to 0.03 nm and the Debye temperatures from 0 to 80 K. The proposed new characteristics are integral and differential concentration coefficients, the magnitude and sign of which can predict concentration dependences for the lattice parameter and the Debye temperature.

Electromagnetic wave absorption of polymer derived ceramic composites tuned by multi-component oxide solid solution

Polymer-derived ceramics (PDCs) are important ceramics for high temperature electromagnetic wave (EMW) absorption because of their tunable conductivity with the pyrolysis temperature. However, it is usually difficult to tune the dielectric properties of the PDCs by only controlling the content of absorption phase in the material system for the purpose of acquiring a wide EMW absorption band. In this work, we illustrate that the PDCs with wide-band high temperature absorption can be obtained through the synergistical tuning by multi-component oxide solid solution (MOS), nano ZrB2 and the metamaterial structure design. The PDCs were prepared by co-pyrolyzing the SiOC precursor, nano ZrB2 and MOS. The MOS helps to tune the permittivity of the PDCs without decreasing the conduction loss of the composites. The effective absorption band (lower than −10dB) of the metamaterial structure made by the prepared ceramic composites exceeds 12 GHz at the frequency range of 2–18 GHz from room temperature (RT) to 1000 °C, revealing a stable high temperature EMW absorption. The metamaterial structure shows good absorption in low frequency range at high temperatures, almost covering the entire S band from RT to 700 °C. The average EM absorption of the ceramic composites is lower than −15dB in the range of 2–18 GHz from RT to 1000 °C. The lowest reflection loss (RL) of the metamaterial is −45dB at 1000 °C. This study successfully address the challenge of simultaneously keeping impedance matching and retaining the strong attenuation of ceramic composites, greatly widening the high temperature EMW absorption band of PDC composites.

Microstructure, thermal/mechanical properties and corrosion behaviors of ternary and quaternary equimolar rare-earth monosilicates

The properties of rare-earth (RE) monosilicates can be regulated by solid solution engineering based on the mixture rule. The combination and number of RE principals are critical factors for better performances. In the present study, four single-phase equimolar multicomponent RE-monosilicate solid solutions including (Dy1/3Er1/3Yb1/3)2SiO5, (Ho1/3Er1/3Yb1/3)2SiO5, (Y1/4Er1/4Tm1/4Lu1/4)2SiO5 and (Dy1/4Er1/4Tm1/4Yb1/4)2SiO5 were synthesized by solid-state reaction and hot-pressing method. The microstructures, thermal and mechanical properties, and corrosion resistance to high-temperature water vapor were systematically investigated. Compared to the single-principal and ternary RE-monosilicates, the quaternary RE-monosilicates exhibited lower thermal conductivity of 1.32 Wm−1K−1 at 400 °C, matched thermal expansion coefficients (3.3 × 10−6/oC ∼ 5.8 × 10−6/oC from 200 °C to 1000 °C) with SiC, and much lower weight loss during water vapor corrosion. The results indicate that the increase of the RE element number can promote the grain growth, lower the thermal conductivity and thermal expansion coefficient, and enhance corrosion resistance.

Preparation, thermophysical properties, and thermal shock resistance of Yb2O3-doped YSZ coatings

The yttria-stabilized zirconia (YSZ) coatings were doped with various concentrations of Yb2O3 to build a multi-component solid solution system. The effects of concentration on the phase composition, microstructure, phase stability at high temperatures, thermal conductivity, thermal expansion, fracture toughness, elastic modulus, and other thermophysical properties of the coatings were systematically analyzed. Furthermore, the mechanism through which Yb2O3 doping impacts the thermal shock resistance of YSZ coatings was elucidated. The results reveal that doping with Yb3+, which has a similar radius to Zr4+, allows the YSZ coatings to retain the tetragonal phase structure at low doping concentrations. The Yb2O3 doping can reduce the thermal conductivity of YSZ coatings due to replacement atom and oxygen vacancy defects enhancing phonon scattering and decreasing the mean free path of phonons. The 1YbYSZ coating demonstrates better thermal shock resistance owing to its high CTE and high fracture toughness resulting from its tetragonal phase, high elastic modulus and high grain boundary density. The Yb2O3 doping can form defect clusters and increase the cation diffusion path due to oxygen vacancies, which inhibits the uneven diffusion of Y3+. Therefore, Yb2O3-doped YSZ coatings demonstrate remarkable phase stability at high temperatures of 1700 °C.

Hardening of multi-component CdZnTeSe solid solutions: a theoretical approach

Hardening of multi-component CdZnTeSe solid solutions: a theoretical approach

“Anomalous” diffusion in multi-layer silicide systems

The transition metal silicide coatings have excellent oxidation resistance. In the high-temperature oxidization environment, the “anomalous” diffusion phenomenon of the reverse concentration gradient occurs in the multilayer silicide coating structure, which has a significant impact on the coating degradation. This study is to explore the physical mechanism of “anomalous” diffusion phase transformation in the MoSi2–NbSi2 bilayer silicide coating on the Nb alloy substrate. Through vacuum annealing experiments, combined with micro-Raman spectroscopy and electron probe microanalysis measurements, the diffuisonal phase transformation of multilayer silicide coating in the oxygen-free environment at high temperatures was studied. By decoupling the oxidation and diffusion, the experiments indicate that high-temperature oxidation is not the dominant driving factor for the “anomalous” diffusion of atoms. The thermodynamic analysis reveals that the reduction in the nucleation barrier of the silicide-poor layer due to multicomponent solid solution and the non-uniform distribution of component chemical potential provide the driving force for the “anomalous” diffusion growth. Based on the diffusion kinetic modeling, the simulation of diffusion-controlled phase transformation in multilayer silicide coating was carried out, and the effect of tracer diffusion coefficients on the growth of the silicide-poor phase was analyzed. The research will have guiding significance for the recognition of failure mechanisms of silicide coating systems and performance improvement.

Chemical durability of multicomponent lanthanide zirconate solid solutions

Multicomponent zirconate solid solutions A2Zr2O7 (A= (Sm,Yb), (Sm,Yb,Gd), (Sm,Yb,Gd,Er), and (Sm,Yb,Gd,Er,Dy)) were synthesized through spark plasma sintering and their chemical durability was investigated via semi-dynamic leaching tests in pH = 1 nitric acid at 90 °C. Incongruent dissolution occurred for all samples with the preferential elemental release of zirconium in all A2Zr2O7 except for high entropy (Sm,Yb,Gd,Er,Dy)Zr2O7 which displays a congruent release of the A-site elements and Zr. A strong positive correlation was found between the lanthanide elemental release rates and the A-site cation size disorder, whereas a negative correlation was observed between the elemental release rates and mixing entropy.

The Role of Te, As, Bi, and Sb in the Noble Metals (Pt, Pd, Au, Ag) and Microphases during Crystallization of a Cu-Fe-S Melt

Quasi-equilibrium directional crystallization was performed on a melt composition (at. %): 18.50 Cu, 32.50 Fe, 48.73 S, 0.03 Pt, Pd, Ag, Au, Te, As, Bi, Sb, and Sn, which closely resembles the Cu-rich massive ores found in the platinum-copper-nickel deposits of Norilsk. Base metal sulfides (BMS) such as pyrrhotite solid solution (Fe,Cu)S1±δ (Poss), non-stoichiometric cubanite Cu1.1Fe1.9S3 (Cbn*), and intermediate solid solution Cu1.0Fe1.2S2.0 (Iss) are progressively precipitated from the melt during the crystallization process. The content of noble metals and semimetals in the structure of BMS is below the detection limit of SEM-EDS analysis. Only tin exhibits significant solubility in Cbn* and Iss, meanwhile Pt, Pd, Au, Ag, As, Bi, Sb, and Te are present as discrete composite inclusions, comprising up to 11 individual phases, within their matrices. These microphases correspond to native Au, native Bi, hessite Ag2Te, sperrylite Pt(As,S)2, hedleyite Bi2Te, michenerite PdTeBi, froodite PdBi2, a solid solution of sudburite-sobolevskite-kotulskite Pd(Sb, Bi)xTe1−x, geversite PtSb2, and a multicomponent solid solution based on geversite Me(TABS)2, where Me = Σ(Pt, Pd, Fe, Cu) and TABS = Σ(Te, As, Bi, Sb, Sn). Most of the inclusions occur as thin layers between BMS grain boundaries or appear drop-shaped and subhedral to isometric grains within the sulfide matrix. Only a small fraction of the trace elements form mineral inclusions of sizes ≤ 0.5 μm in Poss, most likely including PtAs2 and (Pt,Pd)S. It is likely that the simultaneous presence of noble metals (Pt, Pd, Au, Ag) and semimetals (As, Te, Bi, Sb) in the sulfide melt leads to the appearance of liquid droplets in the parent sulfide melt after pyrrhotite crystallization. The solidification of droplets during the early stages of Cbn* crystallization may occur simultaneously with the cooling of later fractions of the sulfide melt, resulting in the formation of Iss. In addition, abundant gas voids containing micro-inclusions were observed in Cbn* and Iss. These inclusions showed similar chemical and mineral compositions to those in BMS matrices, i.e., the presence of gas bubbles did not affect the main features of noble metal fractionation and evolution. Therefore, it is reasonable to assume that ore particles suspended in the melt are either trapped by defects at the crystallization front or transported towards gas bubbles via the Marangoni effect.

Phase Formation and Properties of Multicomponent Solid Solutions Based on Ba(Ti, Zr)O3 and AgNbO3 for Environmentally Friendly High-Efficiency Energy Storage

This paper investigates the processes of phase formation of solid solutions of (1 − x)BaTi0.85Zr0.15O3 − xAgNbO3 where x = 0, 0.03, 0.06, 0.09. The optimal temperatures of synthesis and sintering are determined. From the results of X-ray diffraction analysis, it follows that all solid solutions have a perovskite-type structure. Analysis of the microstructure showed that the average grain size decreases at concentrations x = 0.03 and 0.06. Correlations between the cationic composition and dielectric characteristics of the studied solid solutions have been established. The values of the total stored energy and efficiency are determined. The maximum stored energy was found for a solid solution with x = 0.03 and amounted to 0.074 J∙cm−3 with an efficiency of 76.5%.

Synthesis and strengthening mechanism of (Ti0.9Nb0.03Ta0.03W0.03)3SiC2/Al2O3 composite ceramics by doping NbC, TaC and WC powders

Multi-component solid solution composite ceramics (Ti0.9Nb0.03Ta0.03W0.03)3SiC2/Al2O3 were fabricated with a high yield by doping NbC, TaC and WC powders via in-suit synthesis, which demonstrated that using metallic carbide as dopants is more efficient than using metal powders to synthesize the desired products. The optimized hardness and flexural strength of (Ti0.9Nb0.03Ta0.03W0.03)3SiC2/Al2O3 were measured to be 16.6 ± 0.5 GPa and 695 ± 29 MPa, respectively, which represents significant improvements compared to Ti3SiC2/Al2O3 composite ceramics. To deeply understand the influence of dopants, the crystal structure of multi-component solid solutions and interface modeling of composite ceramics were built and evaluated by first-principle calculations. The results indicated that the strengthening effects derived from both intragranular improvements in solid solutions and intergranular enhancement of crystal interfaces.

Preparation and Mechanical Characteristics of Multicomponent Ceramic Solid Solutions of Rare Earth Metal Oxides Synthesized by the SCS Method

A study into the use of the Solution Combustion Synthesis (SCS) method with glycine and citric acid to synthesize fine powders of multicomponent solid solutions of oxides of rare earth (RE) metals (Nd, Sm, Eu, Gd, Dy, and Ho) for the preparation of ceramic materials is presented. Synthesis parameters of 4-, 5-, and 6-component entropy-stabilized rare earth oxides (REOs) with a C-type cubic structure are determined. The stability of entropy-stabilized oxides (ESOs) with a C-type structure is shown to depend not only on heavy RE metal quantity, but also on the rate of heating/cooling of the samples. The temperature of the polymorphic transformation of C-type REO structures into B-type (monoclinic) or H-type (hexagonal) structural variants can be described by the equation T (°C) = 0.0214Vcr2 − 62.737Vcr + 46390, where Vcr is the unit cell volume of an oxide with a C-type structure regardless of the number of cations in the solid solution. High-temperature thermal analysis up to 1250 °C revealed that dispersed powders, which contain impurities of basic carbonates along with hydroxocarbonates of RE metals and X-ray amorphous carbon formed during SCS reactions, also react with air moisture during storage. The influence of the ESO phase and cationic composition on the morphology, porosity and microhardness of ceramics was studied. Higher-entropy oxides form samples with higher density, microhardness and a smaller size of particle agglomerates.

Modular development of deep potential for complex solid solutions

The multicomponent oxide solid solution is a versatile platform to tune the delicate balance between competing spin, charge, orbital, and lattice degrees of freedom for materials design and discovery. The development of compositionally complex oxides with superior functional properties has been largely empirical and serendipitous, in part due to the exceedingly complex chemistry and structure of solid solutions that span a range of length scales. The usage of classical molecular dynamics (MD), a powerful statistical method, in computer-aided materials design has not yet reached the same level of sophistication as that in computer-aided drug design because of the limited availability and accuracy of classical force fields for solids. Here, we introduce the strategy of ``modular development of deep potential'' (ModDP) that enables a systematic development and improvement of deep-neural-network-based model potential, termed as deep potential, for complex solid solutions with minimum human intervention. The converged training database associated with an end-member material is treated as an independent module and is reused to train the deep potential of solid solutions via a concurrent learning procedure. We apply ModDP to obtain classical force fields of two technologically important solid solutions, ${\mathrm{Pb}}_{x}{\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{TiO}}_{3}$ and ${\mathrm{Hf}}_{x}{\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$. For both materials' systems, a single model potential is capable of predicting various properties of solid solutions including temperature-driven and composition-driven phase transitions over a wide range of compositions. In particular, the deep potential of ${\mathrm{Pb}}_{x}{\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{TiO}}_{3}$ reproduces a few known topological textures such as polar vortex lattice and electric dipole waves in ${\mathrm{PbTiO}}_{3}/{\mathrm{SrTiO}}_{3}$ superlattices, paving the way for MD investigations on the dynamics of topological structures in response to external stimuli. MD simulations of ${\mathrm{Hf}}_{x}{\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ reveal a substantial impact of composition variation on both the phase transition temperature and the nature of the high-temperature nonpolar phase.