Transition Metal Elements Research Articles

First principle calculation of thermoelectric transport performances of new dual transition metal MXene

The quantum restriction effect of charge carriers in two-dimensional materials can significantly improve their power factors. MXene, as a new type of two-dimensional double transition metal material, has attracted extensive attention due to thermoelectric properties, and higher controllability than single transition metal MXene, which has potential applications in thermoelectric devices. In this work, new two-dimensional monolayer double transition metal MXene, i.e. TiZrCO<sub>2</sub> and VYCO<sub>2</sub>, are designed and their stabilities, electronic and thermoelectric properties are studied by the first principles and Boltzmann transport theory. It has been shown that both are indirect bandgap semiconductors with mechanical, thermodynamic and kinetic stability, and their thermoelectric properties (Seebeck coefficients, electrical and electronic thermal conductivities and lattice thermal conductivities) in a temperature range from 300 K to 900 K are studied. For the optimal carrier concentration at 300 K, the p-type TiZrCO<sub>2</sub> power factor is 11.40 mW/(m·K<sup>2</sup>), much higher than that of n-type one, and the VYCO<sub>2</sub> power factor of p-type (2.80 mW/(m·K<sup>2</sup>)) and n-type (2.20 mW/(m·K<sup>2</sup>)) are similar to each other. At 300 K, TiZrCO<sub>2</sub> and VYCO<sub>2</sub> have low lattice thermal conductivities of 5.08 W/(m·K) and 3.22 W/(m·K), respectively, and the contributions of optical phonon to the lattice thermal conductivity are both about 30%, i.e. 2.14 W/(m·K) and 1.09 W/(m·K) at 900 K, respectively. At the same time, it is found that at 300 K, when the material sizes of TiZrCO<sub>2</sub> and VYCO<sub>2</sub> are within 12.84 nm and 5.47 nm respectively, their lattice thermal conductivities are almost unchanged, and can be adjusted by adjusting the compositions. At 900 K, the thermoelectric value of p-type TiZrCO<sub>2</sub> and VYCO<sub>2</sub> reach 1.83 and 0.93, respectively, which are better than those of n-type, 0.23 and 0.84. The double transition metals MXene TiZrCO<sub>2</sub> and VYCO<sub>2</sub> have better thermoelectric properties than the single transition metal MXene (such as Sc<sub>2</sub>C(OH)<sub>2</sub>, <i>ZT</i> = 0.5), and have the potential applications in new thermoelectric materials with excellent comprehensive properties. A set of calculation methods used in this paper can also provide some reference for exploring the thermoelectric properties of a new double transition metal element MXene.

Hypercoordinated Si/Ge driving excellent HER catalytic performance in new TM2X (X = Si and Ge) monolayers: a high-throughput investigation by screening transition metal elements

Constructing relevant transition metal silicides/germanides with planar hypercoordinated Si/Ge can be a new and effective strategy for achieving nonprecious and highly efficient HER catalysts.

First-principles study of magnetic properties and electronic structure of 3d transition-metal atom-adsorbed SnSSe monolayers.

We investigated the electronic structure and magnetic characteristics of 3d transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) adsorbed onto monolayer SnSSe by employing first-principles calculations. After the calculation, we found that Sc, Ti, V, Cu, and Zn atoms adsorbed onto monolayer SnSSe do not have magnetic moments, while the rest of the atoms adsorbed onto SnSSe are able to produce magnetic moments, and their magnetic moments in the adsorption systems are in the range of 1.0-3.0 μB, in which the magnetic distance of Mn is the largest. The results of MAE calculations indicate that there is a big difference in the MAE of the systems with TM atoms adsorbed to the S-side and the Se-side; for V adsorbed to the S-side on the Sn atoms, the MAE is the largest, which reaches 8.277 meV f.u.-1, showing an in-plane magnetic anisotropy, and for Co adsorbed to the Se-side on the Sn atoms, the MAE is the smallest, which is -0.673 meV f.u.-1, showing a perpendicular magnetic anisotropy. Calculations of binding energies show that all atoms are able to adsorb stably. Our results indicate the potential application of TM-adsorbed SnSSe monolayers in spintronics and magnetic memory devices.

Transition metal element doping to optimize the photochromic properties of WO3

This research prepared a photochromic material of WO3 doped with Mo or Cu through a solvothermal method. The material exhibits selective absorption of UV light in the 200–350-nm range. The crystal structure of WO3 remained unchanged after doping, but the bandgap was reduced, thereby increasing its coloration rate. The doping of Mo or Cu brought different new features to WO3: Mo-doping imparted a purple hue upon UV irradiation, whereas Cu-doping accelerated the bleaching of WO3 due to its multi-valent state. WO3-0.1Mo and WO3-0.1Cu were preferentially selected through a practical photochromic process and bandgap calculations, and further used to prepare photochromic ink. This ink is suitable for the preparation of writing and photochromic rewriting paper and retains good photochromic properties even after 50 uses.

Structure-activity relationship study of high entropy oxides catalysts for oxygen evolution reaction

High entropy oxides (HEOs) are promising catalysts of oxygen evolution reactions (OER) in water splitting. However, multi-components, complicated phases and numbers of defects make a lack of deep understanding to the structure–activity relationship of HEOs catalysts. In this paper, different transition metal elements of Fe, Cr, Mn, Mg and Al were doped into (CoNiCuZn)O to form five quinary HEOs. To explore the structure–activity relationship of OER catalysts of HEOs, the phase structure, element valence, oxygen vacancies and electronic structure were characterized and their OER performance was tested. The results show that among all the HEOs, (FeCoNiCuZn)O has the optimal OER catalytic performance: an overpotential of 323 mV at a current density of 10 mA cm−2 in 1 M KOH solution, a Tafel slope of 64.5 mV dec-1, maintaining a high stability for at least 50 h. Its superior OER performance can be attributed to a combination of three main factors: an appropriate band gap of transition metal (TM) 3d and oxygen (O) 2p, a high concentration of oxygen vacancies and a spinel phase precipitation. Among them, the band gap of TM 3d and O 2p showing a volcano relationship with the intrinsic OER activity can be the most decisive descriptor of the intrinsic OER activity of HEOs. A moderate band gap of TM 3d and O 2p being tuned by various cations will lead to more reasonable intermediate adsorption and desorption abilities of HEOs.

Element-configuration dependent first-principles machine learning studies of multiple alloying effects on the structure stability of Co3(Al, W)

Multiple alloying is desired to improve the stability of metastable Co3(Al, W) of Co-based superalloys. However, computational studies of alloying effects are costly due to the enormous combinations of compositions and configurations. Most current element-based machine learning methods that rely solely on composition lack the ability to distinguish between polymorph materials and various local alloying configurations. In this work, we developed efficient machine learning (ML) models using element-configuration dependent Center-Environment (CE) and element-based Chemical Composition (CC) features to describe alloying element type and substitution configuration, crucial for data-driven study of correlated alloying effects and local short-range chemical ordering. We employed first-principles computation and ML methods to investigate the structure stabilities of the Al-W substitution site models with 3d and 4d transition metal (TM) elements, then the optimized ML models were validated using the untrained dual-Al or dual-W site configurations with 3d, 4d, and 5d TM elements. The ML-CE models were generally more accurate than the ML-CC models. The most stable substitution pairs are Sc-Fe 3d TM elements at the Al-W and dual-W sites with lattice constant ∼4 Å. Therefore, we propose a “Co-left” design rule to stabilize Co3(Al, W) by multiple alloying with early 3d TM elements (IIIB-VIII group). The stabilizing 3d “Co-left” elements also can improve the mechanical properties. The ML-CE approach can be generally applied to study local correlated alloying effects and chemical ordering in medium/high-entropy or amorphous alloys.

The Influence of Substitutional Defects of Transition Metal Elements on the Stability and Thermal Properties of Al at Finite Temperatures: A First-Principles Study

Based on first-principles calculations, the effects of substitutional defects of the 3d–5d transition metal elements TMAl on the stability and thermal conductivity of the aluminum matrix were investigated. The results show that with an increase in the atomic number of TM, the defect-forming energy Ef of TMAl exhibits a periodic change feature, which depends on the valence electron configuration of the TM elements. The thermodynamic property parameters calculated with the Debye theory show that the addition of TM atoms does not change the stability of an Al system and can effectively reduce the thermal expansion coefficient of the material. But the equilibrium lattice constant a0 of Al-TMAl supercells changes very little. As the temperature increases, the relaxation time τ decreases, and both the electronic thermal conductivity κe and the total thermal conductivity κ decrease at the temperature range of 100–200 K, followed by a small increase or decrease. Because the lattice thermal conductivity κl is very small in the whole temperature range, the changes in electronic thermal conductivity and total thermal conductivity are basically the same. Moreover, when 1 at.% TM was added at both 300 K and 600 K, it was found that the influence of TM solute atoms on the thermal conductivity κ of Al was much greater than that of the second-phase particles. For solid solution atoms, Pd and Pt atoms have the greatest influence on the thermal conductivity of pure Al. This work is helpful for designing high-performance, heat-resistant Al-based alloys.

Optimization of the First-Principles Calculation Conditions of d3 Ions in SrTiO3

Since transition metal ions are generally more stable in supply than rare earth ions and are inexpensive, researches on alternative materials based on transition metal elements to those based on rare earth elements are actively conducted. As phosphors using transition metal ions, Cr3+ and Mn4+ with d3 configuration are used for red emission while Mn2+ with d5 configuration is used for green emission. For theoretical search of novel phosphor materials, first-principles calculations of the transition energies based on the cluster approach are useful. However, in order to establish an efficient and effective method for prediction, optimization of computational conditions is indispensable.In this study, first-principles calculations of the d-d transition energies of d3 ions such as Cr3+ and Mn4+ in SrTiO3 were performed using the discrete-variational multi-electron (DVME) method. The clusters with Ti4+ at the center were constructed based on the crystal structure data of SrTiO3, and then Ti4+ was replaced with Cr3+ or Mn4+. In order to determine an appropriate cluster size, model clusters consisting of 7, 15, 63, 89, 143, 199, and 391 atoms were constructed. In order to improve the accuracy, the first-principles calculations were carried out considering the configuration-dependent correction (CDC) and the correlation correction (CC), which correct the overestimation of the multiplet energies. The effect of the lattice relaxation was also considered based on the structural optimization using the CASTEP code. Then the cluster size dependence and the effect of the lattice relaxation were clarified based on the detailed comparison of the first-principles calculation results.

Synthesis of FeNi-based heterostructure on a nickel foam at room temperature for efficient catalyzing hydrogen evolution reaction

The FeNi-based heterostructure was synthesized on a nickel foam by a simple dip-coating method with zero-energy consumption at room temperature. The obtained heterostructure is flower-like and has high-performance for electrocatalyzing the hydrogen evolution reaction (HER). On the FeNi-based heterostructure, the overpotential was only 228 mV at a current density of 100 mA cm−2 in 1 M KOH, and can maintain 10 h stability with chronoamperometry test. The outstanding catalytic activity was attributed to the unique structure with a large electrochemical active surface area and the synergistic effect between different transition metal elements. This research afforded a new way to design low-cost and high-performance HER electrocatalyst.

Research progress on hydroxide fluoride-based electrode materials for supercapacitors

Supercapacitors have attracted much attention due to their high-power density and long cycle life, making them a potential substitute for traditional batteries. Research on hydroxide fluorides as electrode materials for supercapacitors has been increasing. Hydroxide fluorides exhibit higher specific capacitance due to the redox reactions between transition metal elements in different oxidation states. However, their high resistance limits their rate performance and cycling stability, which hinders their large-scale application. This article summarizes the main synthesis methods of hydroxide fluorides, and by controlling the reaction conditions, hydroxide fluorides with different morphologies and structures can be obtained to meet various application requirements. In addition, considering the limitations of hydroxide fluorides, this article systematically introduces the main approaches to improving their electrode performance and summarizes the electrochemical characteristics and latest research progress of hydroxide fluorides.

Electronic and elastic correlations in AlB2-type two-dimensional hexagonal MBenes

With the advent of MXenes as two-dimensional (2D) materials beyond graphene, non carbonic 2D materials analogically referred as MBenes have significantly attracted researchers’ attention. Such 2D MBenes remains largely unexplored. Here, we systematically investigate electronic and elastic properties of 2D transition metal (TM) based AlB2-type hexagonal MBenes consisting of a honeycomb networked graphene like boron layer embedded with diverse TM atoms at center. First we determine the thermodynamic, dynamic, thermal, and mechanical stability of MBenes, considering a wide range of 3d, 4d, and 5d TM elements. Electronic and elastic calculations are performed for stable MBenes in order to parameterize and investigate the interdependence of properties. Elastic calculations predicts the brittle-ductile nature and bond character of MBenes while unraveling the in-plane auxetic behavior. Our electronic calculations predict the metallic band nature for 2D VB2, NbB2, TaB2, and WB2 along with previously reported dirac points in 2D TiB2, FeB2, ZrB2, and HfB2. The elastic and electronic calculations clearly indicates the non-directional metallic bonds and intrinsically ductile nature of 2D-FeB2 distinct from other MBenes. Subsequently we performed a covariance analysis to assess the correlation amongst the observables of interest and further establish the interdependence of the properties. Our calculations for elastic correlations also suggests that mechanical brittle-ductile nature and auxetic behavior of MBenes can be tuned by strain engineering of the elastic constants. Our results further suggests that strong correlations between Poisson ratio and d state electrons can be utilized to tune the auxetic behavior by careful doping of the materials. Our work demonstrates the weak elastic-electronic correlations, suggesting that the strain engineering can be utilized for the tailored behavior of MBenes for practical applications. Thus, our systematic analysis of the mechano-elastic and electronic properties of 2D hexagonal MBenes and their correlations advance our understandings of emergent 2D family.

The dynamics of glassy behavior in SrRu1-xFexO3 heterostructure

We report the magnetic interactions in SrRu1-xFexO3 epitaxial thin films. All the films showed a single-phase and good step-terrace structure with minimal surface roughness. The X-ray photoelectron spectra of Fe and Ru revealed that both transition metal elements exist in the films as Fe3+ and Ru4+. With Fe doping, the itinerant ferromagnetic behavior and ferromagnetic transition temperature gradually decreased, but the coercivity field increased. The magnetic interplay between Fe3+-O-Fe3+ is coined as antiferromagnetic. There was another interaction between Ru4+-O-Fe3+ which is best described as ferromagnetic. Furthermore, the magnetic frustration in our films caused by the doped Fe resulted in dynamic glassy behavior. On the other hand, the epitaxial strain from the imminent SrTiO3 substrate along with change in oxygen vacancy might have strong evidence for the spin-glass nature in our thin films.

High‐entropy (Ti0.2V0.2Nb0.2Mo0.2W0.2)Si2 with excellent high‐temperature wear resistance

AbstractThe oxidation products (MoO3 and V2O5) have low melting points and tend to sublimate at high temperatures despite that MoSi2 and VSi2 may possess good self‐lubricating properties. To cope with this challenge, a high‐entropy transition metal disilicide was designed in this work in which transition metal elements that could form high melting point oxides were deliberately added. The high‐entropy (Ti0.2V0.2Nb0.2Mo0.2W0.2)Si2 (HE‐MSi2) with hexagonal structure was successfully prepared by SPS using Ti, V, Nb, Mo, W, and Si powders as the initial materials in this work. The HE‐MSi2 presents a high hardness (11.8 ± 0.4 GPa) and elastic modulus (387.2 ± 46.8 GPa). In particular, its hardness is higher than that of the corresponding disilicides. Noteworthy, HE‐MSi2 demonstrated superior wear resistance when compared to Mo‐Si‐based ceramics (such as MoSi2, Mo5Si3, and Mo5SiB2), high‐entropy carbides (such as (MoTaWVTi)C, (HfMoNbTaTi)C, and (TiVNbMoW)4.375, and traditional single‐phase ceramics (including Sialon, Si3N4, Al2O3, SiC, and ZrO2). Meanwhile, at a high temperature of 600°C, the friction coefficient and wear rate were reduced to 0.64 ± 0.05 and (1.88 ± 0.15)×106 mm3/N·m, respectively. The preferential oxidation of different elements of the HE‐MSi2 was validated through systematical characterization of composition evolution, which was dominantly impacted by high temperature and friction induction.

Influence of Transition Metal Elements on Ni Migration in Solid Oxide Cell Fuel Electrodes

In the present study, the electrochemical performance and microstructure evolutions of Ni-M (M = Fe, Cu, Mn) bimetallic fuel electrodes were investigated under SOFC and SOEC operations. Ni-Fe, Ni-Mn, Ni-Cu and pure Ni patterned fuel electrodes were sputtered on YSZ pellets. During the SOFC tests, the electrochemical performance of all Ni-M bimetallic fuel electrodes were lower than pure Ni electrode, while the degradation rates of Ni-Fe and Ni-Mn electrodes were smaller than the others. The spreading of Ni film on YSZ surface was observed for all samples, and such Ni migration was suppressed by Fe and Mn addition, whereas it was enhanced by Cu addition. During the SOEC tests, the cell performance degraded with Cu and Fe addition, but improved with Mn addition. The adhesion between Ni film and YSZ substrate was enhanced by doping Fe and Mn, which correlated well with the inhibited degradation in both fuel cell and electrolysis operations. The Ni migration phenomenon is discussed by the strength of Ni-O bond, surface tension and melting point, which are influenced by the addition of transition metal elements.

Interfacial synergy between Pt3Co nanoparticles and CoO for efficient ammonia borane hydrolysis

Ammonia borane (AB, NH3BH3) with the high H2 content has been regarded as a promising material for chemical hydrogen storage. AB can hydrolyze to release H2 under the catalysis of noble-metal catalysts with high activity, but the high cost of noble-metals and their poor long-term stability prohibit the large-scale applications. Developing more cost-effective and stable catalysts by introducing cheap transition metal elements has been a promising strategy. Herein, we adopted a step-by-step precipitation method to synthesize bimetallic Pt-Co catalysts supported on rutile TiO2, which show significantly improved performance in AB hydrolysis reaction. The optimized 0.9Pt3.5Co/TiO2 catalyst (with the Pt and Co loadings of 0.9 and 3.5 wt%, respectively) exhibits an extremely high H2 generation rate, showing a turnover frequency value of 2163 molH2 molPt-1 min−1 at 298 K, 9 times higher than that of 0.9Pt/TiO2 catalyst and superior to those of most of the reported Pt-based catalysts. Structure characterizations and theoretical calculations reveal that the promoted AB hydrolysis performance arises from the interfacial synergistic effect between the supported Pt3Co alloy and cobalt oxide CoO, which accelerates the B-H bond cleavage and water activation, respectively. The excellent AB hydrolysis performance of the Pt-Co catalysts indicates the great prospects of alloy-oxide interfaces in the field of liquid phase chemical hydrogen storage.

Understanding the Formation of Complex Phases: The Case of FeSi2

One of the fundamental goals of materials science is to understand and predict the formation of complex phases. In this study, FeSi2 is considered as an illustration of complex phase formation. Although Fe and Si both crystallize with a simple structure, namely, body-centered cubic (bcc A2) and diamond (A4) structures, respectively, it is rather intriguing to note the existence of two complex structures in the Si-rich part of the phase diagram around FeSi2: α-FeSi2 at high temperatures (HT) with a slight iron-deficient structure and β-FeSi2 (also referred to as Fe3Si7) at low temperatures (LT). We re-analyze the geometry of these two phases and rely on approximant phases that make the relationship between these two phases simple. To complete the analysis, we also introduce a surrogate of the C16 phase that is observed in FeGe2. We clearly identify the relationship that exists between these three approximant phases, corroborated by a ground-state analysis of the Ising model for describing ordering that takes place between the transition metal element and the “vacancies”. This work is further supported by ab initio electronic structure calculations based on density functional theory in order to investigate properties and transformation paths. Finally, extension to other alloys, including an entire class of alloys, is discussed.

Tweaks to intrinsic point defects in ZnO ceramics via MnCO3 and their effect on electrical properties

Transition metal elements are necessary dopants in ZnO ceramics to improve electrical properties by defects engineering. In the present study, the tweaking effect of MnCO3 on the intrinsic point defects, i.e., the zinc interstitial and the oxygen vacancy, are investigated to optimize electrical properties of ZnO ceramics. After analyzing microstructure and dielectric response, it was found that Mn2+ was further oxidized to Mn4+ during sintering and Mn4+ solved into ZnO grains and inhibited the formation of the intrinsic point defects. On the other hand, due to the increase of the interface states contributed by Mn separation at grain boundaries, the barrier width broadened to keep charge neutrality. As a result, although the barrier height decreased from 0.68 eV to 0.54 eV as MnCO3 content increased from 0 mol% to 0.63 mol%, the nonlinear electrical properties were enhanced, that is, the breakdown field increased from 188.47 V/mm to 234.82 V/mm, the nonlinear coefficient increased from 12.87 to 74.76, and the leakage current density decreased from 22.08 μA/cm2 to 0.04 μA/cm2. Combined with the stability during DC aging tests, it is suggested that the optimal content of MnCO3 is 0.38 mol%. The study also indicates that the barrier width is a sensitive parameter in optimizing electrical properties of ZnO ceramics, instead of the sole focus on higher barrier height.

Active MoS2-based electrode for green ammonia synthesis

Nitrogen electro-reduction under mild conditions is one promising alternative approach of the energy-consuming Haber-Bosch process for the artificial ammonia synthesis. One critical aspect to unlocking this technology is to discover the catalysts with high selectivity and efficiency. In this work, the N2-to-NH3 conversion on the functional MoS2 is fully investigated by density functional theory calculations since the layered MoS2 provides the ideal platform for the elaborating copies of the nitrogenase found in nature, wherein the functionalization is achieved via basal-adsorption, basal-substitution or edge-substitution of transition metal elements. Our results reveal that the edge-functionalization is a feasible strategy for the activity promotion; however, the basal-adsorption and basal-substitution separately suffer from the electrochemical instability and the NRR inefficiency. Specifically, MoS2 functionalized via edge W-substitution exhibits an exceptional activity. The energetically favored reaction pathway is through the distal pathway and a limiting potential is less than 0.20 V. Overall, this work escalates the rational design of the high-effective catalysts for nitrogen fixation and provides the explanation why the predicated catalyst have a good performance, paving the guidance for the experiments.

How did submarine volcanic eruptions interact with organic matter to favour hydrocarbon generation in the Bohai Bay Basin, China?

ABSTRACT Based on the geological and geochemical analysis of volcanic rock and their surrounding rocks, combined with palaeontological data and hydrocarbon generation thermal simulation experiments, the mechanism of the impact of volcanic eruptions on the formation of organic matter and hydrocarbon generation in the Dongying Depression is investigated. According to the results, underwater volcanic eruptions play a significant role in promoting biological eruptions and water stratification by introducing heat, minerals, and metal elements. The formation of the basalt source rock symbiotic association went through three evolutionary stages, which were underwater eruption, late eruption, and normal sedimentation. These stages have influenced the generation of hydrocarbons from organic matter in the following ways: (1) The organic acid released from the source rock dissolves the adjacent basalt, and the transitional metal elements in the basalt become activated and enter the source rock, which catalyses the hydrocarbon generation from the source rock. (2) Alteration of olivine in basalt releases hydrogen, improving hydrocarbon generation efficiency of source rock. (3) The existence of a large number of carbonates improves the hydrocarbon generation rate and efficiency of source rocks and reduces the hydrocarbon generation threshold of source rocks.

Late Mesozoic tectonic affinity of the Tengchong Block and southward extension of the Bangong-Nujiang Suture: constraints from Early Cretaceous granitic rocks in western Yunnan, SW China

ABSTRACT The southward extension of the Bangong-Nujiang Suture and the late Mesozoic tectonic affinity of the Tengchong Block have been subject to debate, and the Early Cretaceous magmatism in the eastern Tengchong Block provides a crucial window to address these issues. This paper reports comprehensive petrographic, geochemical, geochronological, and isotopic data of Early Cretaceous granitic rocks from the eastern Tengchong Block. Results show that these granitic rocks consist of monzogranites and granodiorites, with zircon U-Pb ages of 120.4–113.9 Ma. These granitic rocks are characterized by enrichments in large ion lithophile elements (e.g. Rb, U, K) and light rare earth elements, but depleted in high field strength elements (e.g. Nb, Ta, P, Ti), and have negative apatite εNd(t) values (−10.4 to −6.7) and negative zircon εHf(t) values (−11.7 to −1.2). The molar [Al2O3/(CaO + K2O + Na2O)] (A/CNK) values and whole-rock zircon saturated temperatures of the studied monzogranites of 1.04–1.09 and 714–799°C, respectively, indicate that they have I-type granite affinity. The presence of biotite indicative of I-type granite and the observation that P2O5 decrease with increasing SiO2 further indicated that the monzogranites have affinities of I-type granites. The petrography, geochemical and isotopic signatures of the studied monzogranites indicate that they originated from partial melting of mafic lower crustal rocks. The Na-rich granodiorites have elevated Na2O/K2O ratios and Na2O contents of 1.19–2.04 and 3.12–3.47 wt.%, respectively. These granodiorites also have relatively high Mg# values and the transition metal element Cr of 53.3–54.5 and up to 100 ppm, respectively. According to these isotopic and geochemical features and the occurrence of magnesiohornblende, we propose that the Na-rich granodiorites were derived from partial melting of ancient basaltic lower crust, with certain inputs of mantle materials in the magma source. Considering these results as well as published data, we finally propose that the Tengchong Block was likely the southeastern extension of the Lhasa Block and that these Early Cretaceous granitic rocks were formed in the setting of the volcanic arc due to westward subduction of the Bangong-Nujiang Tethys oceanic lithosphere beneath the Tengchong Block.