Amount Of Zr Research Articles

True Stress-Strain Behavior of Al-based Cast Automotive Alloy Under Different Ageing Conditions and the Effect of Trace Zr

A thorough investigation has been carried out on the Al-12Si-1Mg-1Cu-1Ni automotive alloy considering different properties, specially mechanical properties associated with true stress and true strain with Zr addition of trace amount. A commercially available piston is melted to produce the alloy, and trace amount of Zr is added to make another. The base alloy along with the Zr added alloy had been applied to homogenization, solution treatment, quenching, and ageing in order to get the age-hardening response. The alloys have been heat-treated at 25 ºC, 200 ºC, and 300 ºC, respectively, for four hours for attaining the under, peak and over-aged states, respectively. During ageing, Al2Cu and Mg2Si phases are formed in the aluminium matrix leading to peak-aged strength, which is reduced at over-aged state because of coarsening of precipitation and recrystallizing, shown by the tensile and hardness properties. When Zr is added to the alloy, Al3Zr phases appear while casting and heat-treatment, resisting the drop of strength at over-aged state. It is visible in the stress-strain diagram that at over-aged conditions, the alloy with trace Zr shows improved strength and ductility. In the micrographs of Zr added alloy, finer distributed grains are visible through the grain refinement of Zr, which also prevents recrystallization at over-aged conditions. The homogeneity of the grains as a result of the Zr addition's microstructural change was further confirmed by fractography. It is clear that adding Zr to such alloys does not greatly increase their strength, but it does restrict the declining of strength by preventing the production of thermally stable Al3Zr precipitates, which coarsens the resisting behavior of various intermetallics in the thermally damaged alloy.

Enhancing mechanical and photocatalytic properties by surface microstructure regulation of TiO2 nanofiber membranes

In this work, TiO2 nanofiber membrane (NFM) with a complete surface microstructure was prepared through regulating the surface microstructure of TiO2 NFM by doping Zr. The crystal structures and morphological analyses indicated that the nanofiber membranes were consisted by disordered accumulation of Zr-doped TiO2 nanofibers with a crack-free surface, small grain size and high aspect ratio. When the doping amount of Zr was 0.8 mL, the tensile strength of the doped membranes reached 1.27 MPa, which was 60.7% higher than that of pure TiO2 NFM. The photocatalytic performance of Zr-doped TiO2 NFM was evaluated by the degradation performance of Methylene orange (MO) under simulated sunlight irradiation. Compared with the undoped TiO2 NFM, the 0.8-Zr/TiO2 NFM presented a higher catalytic degradation efficiency (improved by 69.6%), and the photocatalytic performance maintained stable after five circulating. It was found that the doping of Zr ions effectively limited the surface crack size and grain size of TiO2 nanofibers, thereby improving the tensile strength, and enhanced the surface area effect and carrier transfer efficiency of TiO2 NFM. On the other hand, a narrow band-gap was obtained by doping a small amount of Zr ions, which expanded the visible light response range to improve the photocatalytic performance of TiO2 nanofibers.

A comparison of the extraction behaviour of tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates for the separation of metal ions for U–Zr and U–Pu–Zr systems by cross-current mode

Abstract Even though, pyroprocessing is considered as a suitable technique for metal fuel processing, attempts are being made in our laboratory to develop a solvent extraction based process as an interim method. Since, the metallic fuels contain considerable amount of Pu(IV) and Zr(IV), the use of conventional extractant tri-n-butyl phosphate (TBP) for reprocessing may pose problems due to third phase formation. In the exploration for the identification of an alternate extractant in the organophosphate family, tris(2-methylbutyl) phosphate (T2MBP), a branched isomer of tri-n-amyl phosphate (TAP) was found to be a potential extractant for nuclear fuel reprocessing. In this context, batch wise extraction and stripping studies with a feed solution containing U(VI) and 6 wt% Zr(IV) were carried out with unirradiated and irradiated 1.1 M solution of T2MBP in n-dodecane (n-DD) and the results were compared with corresponding solutions of TBP and TAP in n-DD. Among all these systems under identical conditions, third phase formation was observed only in the case of irradiated TBP system which makes U–Zr fuel reprocessing difficult using TBP as the extractant. Furthermore, studies have also been carried out with U–Pu–Zr feed solution to understand the extraction and stripping behaviour of these extractants. The stage wise and cumulative percentage of extraction and stripping for each metal ion of these systems were evaluated. Overall, these batch studies indicated that, T2MBP system has comparable extraction and stripping behaviour with U–Zr and U–Pu–Zr feed solutions and T2MBP exhibits better separation factor than TBP.

Effects of Zirconium on the Structure and Mechanical Properties of High‐Strength Low‐Alloy Steels under Quenched or Tempered Conditions

The effects of zirconium (Zr) on the microstructure, inclusions, Vickers hardness, impact toughness, and tensile properties of quenched and tempered high‐strength low‐alloy (HSLA) steels are investigated. The results show that the addition of Zr is beneficial to the refinement of the grain size of HSLA steels under the two heat treatment conditions. When the Zr content is 0.2 wt%, the average grain size of the steel is the smallest. The main inclusions in Zr‐containing HSLA steels are Zr–O and Zr–O–Mn–S, and the distribution of inclusions in HSLA steels is the most uniform when the Zr content is 0.04 wt%. The addition of an appropriate amount of Zr improves the Vickers hardness of HSLA steels under two heat treatment conditions. In terms of impact toughness, the increase of Zr content is beneficial to improving the room‐temperature impact energy of HSLA steels under two heat treatment conditions, but the improvement of the impact properties of tempered HSLA steels is limited. For tensile properties, the addition of 0.04 wt% Zr is beneficial to increasing the strength of quenched or tempered HSLA steels.

Influence of Zr content on immersion and electrochemical corrosion behavior of as-cast TiZr alloys

PurposeThe purpose of this paper is to study the influence of Zr content on immersion and electrochemical corrosion behavior of Zr-containing Ti-based (TiZr) alloys.Design/methodology/approachThe phase analysis of as-cast TχZAB alloys was carried out using X-ray diffraction. The microstructure of corrosion surfaces of the samples was observed using optical metallographic microscopy and scanning electron microscopy, equipped with energy dispersive spectroscopy.FindingsThe immersion test reveals that the corrosion is alleviated in the presence of a high amount of Zr, whereas pitting corrosion occurs when the Zr content is up to 40 Wt.%. Furthermore, the electrochemical analysis demonstrates that the corrosion resistance TiZr alloys is improved with increasing Zr content.Originality/valueThe TiZr alloys are promising candidates for high-end applications because of their excellent comprehensive properties. These alloys are usually used in marine or other harsh corrosive environments; therefore, it is essential to study their corrosion behavior.

Study of Zr addition on the composition, crystallite size, microstructure and properties of high-performance nano Cu alloys prepared by mechanical alloying

Although nanostructured Cu alloys prepared show great advantages in performance, the excellent properties have not been achieved at present primarily due to a single strengthening method or the Fe contamination introduced during mechanical alloying. In the present work, an appropriate amount of Zr was added to adjust the milling process and Fe contamination in the Cu matrix. Then the effects of Zr on the morphologies, crystallite sizes, lattice strain, composition and properties were analyzed. When the added Zr content was 0.1 wt%, it could promote the work hardening of Cu powders, resulting in smaller crystallite sizes, larger internal strain. And a slightly higher Fe content was introduced. However, with the increase of the Zr content, the Fe contamination was reduced obviously and the crystallite size began to increase again. Even so, the average crystallite sizes of nanostructured Cu alloys were still less than 20 nm. The results also showed that MA could increase the solid solubility of Zr in Cu. In a word, the properties of the nanostructured Cu alloys were improved by the refinement strengthening of matrix, solid solution and dispersion strengthening of Fe and Zr. The optimum properties were achieved by Cu-0.1 wt% Zr with electrical conductivity of 75.19% IACS and tensile strength of 526 MPa. The study provided a new route for overcoming Fe contamination in the metal matrix, and further improving the properties of Cu alloys through various strengthening methods.

Effect of Zr content on the physicochemical, electrochemical, and biological properties of Ti80Nb20-based alloys

The β-Ti alloys have become very attractive in the area of biomedical materials due to their corrosion resistance, biocompatibility, and low elastic modulus as compared with other materials. In this context, the Ti-Nb-Zr ternary system has gained more interest because Zr acts as secondary β-Ti stabilizing element when it is added together with β-stabilizing element such as Nb or Mo. According to the d-electron theory, the higher the Zr content, the lower elastic modulus values are obtained, which would allow to produce alloys with low elastic modulus, corrosion resistance, and shape memory. However, determining the ideal amount of Zr in a Ti-Nb-Zr alloy is still a matter of investigation. In this work, alloys with a nominal chemical composition of Ti80−x-Nb20-Zrx (x = 5, 10, 20, 30, and 40 at%) were produced by electric arc casting. The results show that the addition of Zr causes a decrease in both the elastic modulus and the hardness of the molten alloys, reaching values of 50.5 GPa for a sample with 40 at% Zr. The increase in the Zr content caused a microstructural difference between the phases, and the α” phase was detected for the Ti80Nb20, Ti75Nb20Zr5, and Ti60Nb20Zr20 alloys. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the environment influences the Ti-Nb-Zr surfaces, showing the growth of oxide layers, mainly Ti, Zr and, to a lesser extent, Nb oxides. All alloys with different Zr amounts showed wide passivation regions and no sign of pitting in the potential range that is characteristic of the human body. The Ti-Nb-Zr alloys showed good compatibility in cell growth tests, with the best results for the 20 at% Zr alloy, and a decrease in biocompatibility for higher Zr amounts due to reactions of Zr4+ with body fluids.

Crystal nucleation and growth processes in Cu-rich glass-forming Cu-Zr alloys.

The glass formation ability of an alloy depends on two competing processes: glass-transition, on one hand, and crystal nucleation and growth, on the other hand. While these phenomena have been widely studied before in nearly equiatomic Cu-Zr alloys, studies are lacking for solute/solvent-rich ones. In the present work, molecular dynamics simulations show that the addition of a small amount of Zr (1-10 at. %) to Cu drastically increases the incubation time and slows down crystal growth, thus, leading to an improved glass forming ability. The crystal nucleation and growth processes of a competing face-centered cubic (FCC) Cu crystalline phase are analyzed in detail. In particular, the values of the critical cooling rate, incubation period for crystallization, and growth rate of FCC Cu crystals in these Cu-rich alloys are obtained. The growth of a supersaturated FCC Cu solid solution is found to be polymorphic at the interface (except for alloys with 9 and 10 at. % Zr) though a Zr concentration gradient is observed within growing crystals at high enough Zr content. The crystal growth rate before crystal impingement is nearly constant in all alloys, though it decreases exponentially with the Zr content. Crystallization kinetics are also analyzed within the existing theories and compared with the experimental values available in the literature.

Purification and Characterization of High Purity Nano Zirconia by Liquid-Liquid Extraction Using D2EHPA/p-Xylenes

In this paper, Zr(IV) nitrate solution decomposed from Viet Nam zircon concentrate was the source of zirconium extraction by liquid-liquid extraction (L.L.E). The FT-IR and UV-Vis spectra confirmed the extraction of Zr(IV) by D2EHPA/p-xylenes. There were four stages for the purification of impurities from the Zr matrix. First, the extraction of elements in 3.0 M HNO3 by 50% D2EHPA/p-xylenes was conducted. Second, two scrubbing cycles of impurities using 6.0 M HNO3, 76.5% of the total amount of Zr(IV) were retained in the organic phase, and 23.5% remained in the aqueous phase. Third, the stripping of a macro amount of zirconium from loaded D2EHPA has been effectively carried out using 1.5 M H2SO4 with a stripping efficiency of 99.6%. Fourth, concentrated ammonia was added to the solution Zr(IV) after stripping extraction to form precipitate for calcination at 550 °C for the final products. The refined products were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDS, XRF, and diffuse reflectance spectroscopy. The ZrO2 has high purity, is nanospherical, and has a uniform sphere-like morphology with small grain size of less than 30 nm and a bandgap value of about 3.30 eV.

The Role of Zr on Monoclinic and Orthorhombic HfxZryO2 Systems: A First-Principles Study.

HfO2 shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO2 is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P21/c and the orthorhombic Pca21 polymorphs of HfO2, Hf0.75Zr0.25O2, and Hf0.5Zr0.5O2 is reported. For all six systems, density functional theory (DFT) methods based on generalized gradient approximations (GGAs) were first used; then the GGA + U method was settled and calibrated to describe the electrical and optical properties of polymorphs and the responses to the oxygen vacancies. Zr had different effects in relation to the polymorph; moreover, the amount of Zr led to important differences in the optical properties of the Pca21 polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of HfxZryO2 nanostructures. The combined GGA and GGA + U methods adopted in this work generate a reasonable prediction of the physicochemical properties of o- and m-HfxZryO2, identifying the effects of doping phenomena.

In-Situ Visualization of the Transition Metal Dissolution in Layered Cathodes

Abstract Transition metal dissolution in layered cathodes is one of the most intractable issues that deteriorate the battery performance and lifetime. It not only aggravates the structure degradation in cathode but also damages the solid electrolyte interphase in anode and even induces the formation of lithium dendrites. In this work, we investigate the dissolution behaviors of polycrystalline and single-crystalline layered cathode via operando X-ray imaging techniques. The cathode particle morphology appears to have a significant impact on the evolution of the dissolution dynamics. As a mitigation strategy, we reveal that doping with a trace amount of Zr in the layered cathode could improve its robustness against the transition metal dissolution. Our finding provides valuable insights for designing the next-generation highly stable layered battery cathodes.

Optimization of the Zr-loading on siliceous support catalysts leads to a suitable Lewis/Brønsted acid sites ratio to produce high yields to γ-valerolactone from furfural in one-pot

The study for the production of γ-valerolactone from furfural in one-pot has been carried out using ZrO2 supported on silica spheres. The catalysts synthesized were characterized by XRD, UV-vis, HR-TEM, N2 adsorption, IR, pyridine adsorption-IR and NH3-TPD in order to determine their physicochemical characteristics. Both, Lewis and Brønsted acid sites are necessary to produce γ-valerolactone from furfural, because they are involved in different steps of the reaction. Accordingly, a reaction mechanism has been proposed. Lewis acid sites of ZrO2 interacting with the –OH surface groups of the siliceous spheres can generate Brønsted acid sites in the supported Zr catalysts, which are absent in both pure ZrO2 and the silica spheres. Then, by controlling the amount of Zr in the supported catalysts, the relative amount of Lewis and Brønsted acid sites can be optimized to obtain the highest yields to γ-valerolactone. The Zr-loading of the optimal supported catalyst was ca. 7 wt% Zr, which reached a γ-valerolactone yield of 72.4 % after 8 h at 180 °C using 2-propanol as a solvent and hydrogen donor.

Abundance of zirconium in the globular cluster 47 Tucanae: a possible Zr–Na correlation?

We determined abundances of Na and Zr in the atmospheres of 237 RGB stars in Galactic globular cluster (GGC) 47 Tuc (NGC 104), with a primary objective of investigating possible differences between the abundances of Zr in the first generation (1P) and second generation (2P) stars. For the abundance analysis, we used archival UVES/GIRAFFE spectra obtained during three different observing programmes. Abundances were determined from two Na I and three Zr I lines, using 1D hydrostatic ATLAS9 model atmospheres. The target stars for the abundance analysis were limited to those with 4200 ≤ Teff ≤ 4800 K. This is the largest sample of GGC stars in which Na and Zr abundances have been studied so far. While our mean [Na/Fe] and [Zr/Fe] ratios agree well with those determined in the earlier studies, we find a weak but statistically significant correlation in the [Zr/Fe] – [Na/Fe] plane. A comparison of the mean [Zr/Fe] abundance ratios in the 1P and 2P stars suggests a small but statistically significant Zr over-abundance in the 2P stars, ∆[Zr/Fe]2P−1P ≈ +0.06 dex. Also, our analysis shows that stars enriched in both Zr and Na are more centrally concentrated. However, we find no correlation between their distance from the cluster centre and their full spatial velocity, as indicated by the velocity dispersions at different mean values of [Zr/Fe] and [Na/Fe]. While there may be some influence of CN line blends on the determined Zr abundances, it seems very unlikely that the detected Zr–Na correlation, for the slightly higher Zr abundances in the 2P stars, would be caused by the CN blending alone. The obtained results indicate that, in 47 Tuc, some amount of Zr should have been synthesised by the same polluters that enriched 2P stars with the light elements. While sizeable amounts of Zr may be synthesised by both AGB stars (M ~ 1.5–5 M⊙) and massive rotating stars (M ~ 12–25 M⊙, υrot > 150 km s−1), our data alone do not allow us to distinguish which of the two scenarios, or whether or not a combination of both, could have operated in this GGC.

An ab initio simulation and experimental studies of the glass-forming ability and properties of Al86Ni(14-x)Zrx (x = 1∼7) alloys

In this paper, glass-forming ability (GFA) and thermal stability of melt-spun Al-Ni-Zr amorphous ribbons with different Zr content were investigated via X-ray diffraction, transmission electron microscope and differential scanning calorimetry. The electrochemical performance and hardness performance of the ribbons with different amorphous content were analyzed. It is shown that with the addition of Zr, the amorphous content and corrosion resistance first increases and then decreases. However, the hardness of the ribbons with a minor fraction of the amorphous content is the highest. To further study the influence of the Zr element on the GFA of Al-Ni-Zr alloys, ab initio molecular dynamics simulation was used to calculate the atomic structure, coordination number, and Voronoi polyhedron. The calculation results show that adding an appropriate amount of Zr affects the interaction between atoms, causing significant changes in the local structure and increasing the content of the icosahedron to improve the GFA.

Synergistic effect of amino-functionalized SBA-15 in Cu-catalyzed oxidative homocoupling of phenylacetylene

SBA-15 mesoporous silica materials with short mesochannels functionalized with various amino-groups, including NH2-, MeNH-, diamine-, triamine- and guanidine-groups were prepared through one-pot co-condensation of tetraethylorthosilicate (TEOS) and amino-containing trimethoxysilanes in the presence of P123 as pore-directing agent and an appropriate amount of Zr(IV) ions. The resultant materials immobilized with CuCl were examined as reusable catalysts in the oxidative homocoupling of phenylacetylene at room temperature with air as the oxidant. Efforts were made to avoid the liquid base additives. The Cu-guanidine-SBA-15 catalyst with Cu/guanidine molar ratio of 0.6 was found to satisfy this objective and gave the highest yield (up to ca. 97%) and nearly 100% selectivity of 1,4-diphenyl-1,3-butadiyne in 24 h. Moreover, the catalyst could retain around 90% yield after reuses for three times.

Adsorption and separation of flavonoid aglycones and flavonol aglycones by using Zr(IV) immobilized collagen fiber adsorbent as column packing material

Flavonoid aglycones and flavonol aglycones, are difficult to be separated due to their similar structures and limited hydroxyls. Herein, Zr(IV) immobilized collagen fiber (ZCF) was prepared by immobilizing Zr(IV) on glutaraldehyde cross-linked collagen fiber (GCF) to separate apigenin and kaempferol, the representative compounds of flavonoid aglycones and flavonol aglycones. TG, DSC, SEM and element mapping were applied to characterize ZCF. The static adsorption suggested that when the amount of immobilized Zr(IV) reached only 0.3 mmol/g, the adsorption difference between apigenin and kaempferol on ZCF was highly improved compared with GCF without Zr(IV). The adsorption rate of apigenin increased from 2.21% to 14.31%, while that of kaempferol significantly increased from 22.35% to 87.17%. In addition, the spectroscopy (UV–Vis, FT-IR) were applied to analyze the binding sites of flavonoids with Zr(IV), indicating that the strong adsorption of ZCF to kaempferol may be related to the 3-hydroxyl on the C-ring, while apigenin only can conduct a weak binding with ZCF through 5-hydroxyl on the A-ring. In ZCF column chromatography separation, apigenin and kaempferol could be separated effectively with purities of 94.02% and 89.23% by stepwise elution of 50% aqueous ethanol followed by 50% aqueous ethanol containing 0.005 mol/L citric acid. In separation on ZCF and GCF combined columns, the purities of apigenin and kaempferol reached 95.59% and 92.56%, respectively, and the trace amount of Zr(IV) shedding from ZCF was completely adsorbed by GCF avoiding contaminating the target components. In addition, the effective separation of apigenin and kaempferol in apium graveolens (celery) extract by ZCF column was also achieved. The above results indicated ZCF could selectively adsorb flavonol aglycones with 3-hydroxyl on the C-ring from the mixture with flavonoid aglycones. This investigation provides a novel column chromatography packing material for the fast separation of flavonoid aglycones and flavonol aglycones.

Effect of Thermomechanical Treatment of Al-Zn-Mg-Cu with Minor Amount of Sc and Zr on the Mechanical Properties.

In this study, the mechanical and microstructural properties of Al-Zn-Mg-Cu-Zr cast alloy with 0.1% Sc under homogeneous, dissolution, and T6 and thermomechanical treatments with the aim of increasing the volume fraction of MgZn2. Al3(Sc,Zr) reinforcing precipitates were examined by hardness, microscopic examinations, tensile tests and software analysis. The results showed that, firstly, the hardness results are well proportional to the results of the tensile properties of alloys and, secondly, the strength of the alloy with thermomechanical treatments compared to T6 treatments increased from 492 MPa to 620 MPa and the elongation increased from 8% to 17% and was 100% upgraded. Microstructural and fracture cross section investigations showed that Al3(Sc,Zr) nanosize dispersoids were evenly distributed among MgZn2 dispersoids and the alloy fracture was of semi-ductile type and nanosize dispersoids less than 10 nm were observed at the end of the dimples in the fracture section. The volume fraction of nanosize dispersoids in the whole microstructure of thermomechanical treatment samples was also much higher than that of T6 heat treated samples, so that the percentage of Al3(Sc,Zr) precipitates arrived from less than 1% in T6 operation to 8.28% in the quench-controlled thermomechanical operation (with 50% deformation). The quality index (QI) in thermomechanical treatment samples is 19% higher than T6 samples, so that this index has increased from 641 in T6 operation to 760 in samples under thermomechanical treatment due to precipitate morphology, volume fraction of precipitates, their uniform distribution in the matrix, and nano sized precipitates in samples under thermomechanical treatment.

Effect of Zr on solidification and microstructure of a Ni-based superalloy with high Al and Ti contents

The total content of Al and Ti in advanced Ni-based wrought superalloys is up to 7.5wt.%, which makes it easier to form harmful nonequilibrium eutectic (γ+γ′) and η phase. It has been reported that the addition of certain amount of Zr can modify precipitation of the nonequilibrium phases obviously, but the mechanism is still controversial. The effect of Zr ranging from <0.0006wt.% to 0.150wt.% on solidification behavior, segregation and microstructure of a Ni-based superalloy with high Al and Ti contents was investigated, eliminating the interferences of C and B. Results show that increase in Zr content significantly promotes the formation of eutectic (γ+γ′), η and Zr-rich phase in the interdendritic region. Besides the Zr-rich phase, Zr dissolves slightly in the eutectic γ′ and obviously in the η phase. An interesting phenomenon is discovered that the Zr addition significantly increases the area fraction of liquid pools and enlarges the forming range of γ dendrites, which suggests that Zr markedly retards the solidification. Zr affects the eutectic (γ+γ′) and η formation mainly due to the retard of solidification and dissolution of Zr in them. The retard of solidification obviously increases the residual liquid fraction and undercooling. Zr can serve as a forming element for the eutectic (γ+γ′) and η phase, and the obvious dissolution of Zr in η phase significantly decreases the critical concentration of Ti for its precipitation.

Diffusion of zirconium on the surface of Schottky electron sources

The current study investigates the diffusion of a Zr–O complex on a W substrate, which is one of the surface components of the Schottky electron source. To enable the thermal diffusion of Zr atoms with the assistance of oxygen, the source was heated to approximately 1800 K; this enabled the Zr–O complex to reach the electron emission area at the source apex, which was several hundred micrometers away from the Zr reservoir. At such a high temperature, the evaporation rate of surface components also increased, making it more difficult for the atoms to diffuse farther. To better understand the mechanisms underlying diffusion and evaporation, the amount of Zr on the surface was estimated using Auger electron spectroscopy. The surface coverage of the Zr–O complex was found to be almost constant up to 600 μm without any significant loss. Furthermore, the diffusion of the Zr–O complex was found to be more dominant than evaporation, resulting in coverage saturation. However, when coverage of the Zr–O complex decreased, the observed trends changed drastically, which suggests that the balance of diffusion and evaporation cannot be described by a simple material balance equation. Additionally, the range with a fully covered area of the Zr–O complex became narrower at temperatures higher than 1900 K. These features, however, varied depending on the vacuum level surrounding the sample. Based on these findings, the diffusion and evaporation model of Zr and O on the surface of the Schottky electron source is proposed.

Zr-Doped TiO2 Electron Transport Layer for Reduced Hysteresis and Highly Efficient Perovskite Solar Cells

Zr-doped TiO2 electron transport layer for reduced hysteresis and highly efficient perovskite solar cells Chirag Saharan, Pawan S Rana* Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonepat, India, 131039 drpawansrana.phy@dcrustm.orgLarge number of defects in compact TiO2 (c-TiO2) layer hinders the power conversion efficiency (PCE) of hybrid perovskite solar cells (PSCs). Metal doping in c-TiO2 layer has been recognized as a successful approach for boosting the PCE of PSCs. In this work, different amount of Zr is added in c-TiO2 layer and its impact on the photovoltaic properties of methylammonium lead iodide (MAPbI3)-based PSCs is studied. Incorporation of Zr enhanced the charge carrier collection at TiO2/perovskite interface as well as conductivity of TiO2 layer. It is observed that Zr-doping has reduced the dark current significantly by suppressing the leakage path. Consequently, the PSCs with optimal Zr-doping (10 vol%) displays open-circuit voltage (V OC) of 1.076 V, short-circuit current density (J SC) of 23.57 mA cm-2, and PCE of 18.16% under one-sun illumination. From our fundamental study, we confirm that Zr doping in TiO2 is highly beneficial to reduce the hysteresis index (HI) as low as 6.8% in comparison to pristine TiO2 with large HI of 17.9% and it reduces the trap-state density as well as non-geminated recombination losses. Together, our findings will pave the way for engineering the energy level of electron transport layer and fabrication of highly efficient PSCs. Key Words: Hybrid perovskite solar cells; Zr-doping; band alignment, trap-state density, non-geminated recombination losses