Free occupying mechanism of simulated tetravalent waste ions in Gd2Zr2O7 and performance evaluation of the waste forms

To extend the practicability of ceramics in immobilizing nuclear waste with fluctuant composition, structural design should be abandoned. The simulated tetravalent actinide waste An⁴⁺ (Ce⁴⁺) was directly doped into prepared Gd₂Zr₂O₇, and the waste forms were synthesized by high-temperature solid-state reaction. It has been shown that the maximum loading of CeO₂ in Gd₂Zr₂O₇ lies between 20 and 30 wt.%, and Ce elements are uniformly distributed in the matrix. Existing in Ce³⁺ and Ce⁴⁺, cerium ions automatically occupied both the Gd and Zr sites in Gd₂Zr₂O₇ according to valence equilibrium. This occupation causes the change of r(A³⁺)/r(B⁴⁺) and eventually leads to the structure transition from pyrochlore to fluorite. In addition, the normalized leaching rate of the sample with 60 wt.% of dopant was about 2.5 × 10⁻⁷ g m⁻² d⁻¹ on the 35th day. In this study, a free occupation of simulated waste ions in ceramics was proposed.     

The influence of pentavalent Nb substitution for Zr on electrical property of oxide-ion conductor Gd2Zr2O7

Gd₂(Zr_1−xNb_x)₂O_7+x (0 ≤ x ≤ 0.2) ceramics are prepared via the solid state reaction process at 1973 K for 10 h in air. Gd₂(Zr_1−xNb_x)₂O_7+x (x = 0.1, 0.2) ceramics exhibit an ordered pyrochlore-type structure, whereas Gd₂Zr₂O₇ has a defective fluorite-type structure. The electrical property of Gd₂(Zr_1−xNb_x)₂O_7+x ceramics is investigated by electrochemical impedance spectroscopy over a frequency range of 10 Hz to 8 MHz from 623 to 923 K. The electrical conductivity obeys the Arrhenius equation. The grain conductivity of Gd₂(Zr_1−xNb_x)₂O_7+x ceramics varies with doping different Nb contents, and exhibits a maximum at the Nb content of x = 0.1 in the temperature range of 623-923 K. The conductivity in hydrogen atmosphere is a little bit higher than in air in the temperature range of 723-923 K, which indicates that the doping of Zr⁴⁺ by Nb⁵⁺ can increase the proton-type conduction and reduce the oxide-ionic conduction. The conduction of Gd₂(Zr_1−xNb_x)₂O_7+x is not a pure oxide-ionic conductor.     

Phase Evolution and Microstructural Studies in CaZrTi2O7–Nd2Ti2O7 System

A series of compositions with general stoichiometry Ca_1?xZr_1?xNd_2xTi₂O₇ has been prepared by high‐temperature solid‐state reaction of component oxides and characterized by powder X‐ray diffraction and electron probe for microanalyses (EPMA). The phase fields in CaZrTi₂O₇–Nd₂Ti₂O₇ system and distribution of ions in different phases have been determined. Four different phase fields, namely monoclinic zirconolite, cubic perovskite, cubic pyrochlore, and monoclinic Nd₂Ti₂O₇ structure types are observed in this system. The 4M‐polytype of zirconolite structure is stabilized by substitution of Nd³⁺ ion. The addition of Nd³⁺ ions form a cubic perovskite structure‐type phase and thus observed in all the compositions with 0.05 ≤ x ≤ 0.80. Cubic pyrochlore structure‐type phase is observed as a coexisting phase in the nominal composition with 0.20 ≤ x ≤ 0.90. Only a subtle amounts of Ca²⁺ and Zr⁴⁺ are incorporated into the perovskite‐type Nd₂Ti₂O₇ structure. EPMA analyses on different coexisting phases revealed that the pyrochlore and perovskite phases have Nd³⁺‐rich compositions.     

Rapid preparation of Gd2Zr2−xCexO7 waste forms by flash sintering and their chemical durability

A simple and low-energy-consuming approach for preparing ceramic nuclear waste forms is greatly preferred for disposal of ever-increasing amounts of radioactive nuclear wastes. Herein, simulated radionuclide Ce could be rapidly incorporated into Gd₂Zr₂O₇ ceramic via flash sintering technique. Under an electric field of 250 V/cm, Gd₂Zr_2−xCe_xO₇ (0.0 ≤x ≤ 1.2) waste forms with a single phase of defect-fluorite were flash sintered at relatively low temperatures of 889–997 °C in 60 s. The onset temperature of flash sintering was decreased with the enhancement of Ce content. Furthermore, the density and grain size of Gd₂Zr_2−xCe_xO₇ waste forms were increased with the increase of the current limit. The nearly full dense Gd₂Zr_2−xCe_xO₇ waste forms were flash sintered at a current limit of 200 mA. The normalized leaching rates of Gd, Ce, and Zr in Gd₂Zr_0.8Ce_1.2O₇ after 28 d were 6.5475 × 10⁻⁵, 1.1624 × 10⁻⁷, and 1.1613 × 10⁻⁷ g·m⁻²·d⁻¹, respectively, which exhibited a good chemical durability.     

Preparation, characterization and electrical conductivity studies of NdYb1−xGdxZr2O7 (0 ≤ x ≤ 1.0) ceramics

Several compositions of NdYb_1−xGd_xZr₂O₇ (0 ≤ x ≤ 1.0) ceramics were prepared by pressureless-sintering method at 1973 K for 10 h in air. The relative density, microstructure and electrical conductivity of NdYb_1−xGd_xZr₂O₇ ceramics were analyzed by the Archimedes method, X-ray diffraction, scanning electron microscopy and impedance plots measurements. NdYb_1−xGd_xZr₂O₇ (0 ≤ x ≤ 0.3) ceramics have a single phase of defect fluorite-type structure, and NdYb_1−xGd_xZr₂O₇ (0.7 ≤ x ≤ 1.0) ceramics exhibit a single phase of pyrochlore-type structure; however, the NdYb_0.5Gd_0.5Zr₂O₇ composition shows mixed phases of both defect fluorite-type and pyrochlore-type structures. The measured values of the grain conductivity obey the Arrhenius relation. The grain conductivity of each composition in NdYb_1−xGd_xZr₂O₇ ceramics gradually increases with increasing temperature from 673 to 1173 K. NdYb_1−xGd_xZr₂O₇ ceramics are oxide-ion conductor in the oxygen partial pressure range of 1.0 × 10⁻⁴ to 1.0 atm at all test temperature levels. The highest grain conductivity value obtained in this work is 1.79 × 10⁻² S cm⁻¹ at 1173 K for NdYb_0.3Gd_0.7Zr₂O₇ composition.     

An abnormal incorporation behavior of Th in Gd2Zr2O7: A first-principles study

A theoretical study of Th accommodation in Gd₂Zr₂O₇ has been performed by density functional theory. Our calculations show that although thorium has only one charge state of Th⁴⁺, it can be incorporated into both Gd³⁺ and Zr⁴⁺ sites in Gd₂Zr₂O₇, depending on the chemical environments. Th occupation at Gd³⁺ site results in charge redistribution and the excess electrons introduced by Th are transferred to the neighboring Zr ions. As compared with the pure state, Th-containing Gd₂Zr₂O₇ pyrochlores are probably more inclined to undergo order-disorder transformation and are less susceptible to radiation-induced amorphization.     

Effect of CaO addition on the structure and electrical conductivity of the pyrochlore-type GdSmZr2O7

Polycrystalline GdSm_1?xCa_xZr₂O_7?x/2 (0 ≤ x ≤ 0.20) ceramics have been prepared by the solid-state reaction method. The effects of CaO addition on the microstructure and electrical properties of the pyrochlore-type GdSmZr₂O₇ ceramic were investigated. GdSm_1?xCa_xZr₂O_7?x/2 (x ≤ 0.05) ceramics exhibit a pyrochlore-type structure; however, GdSm_1?xCa_xZr₂O_7?x/2 (0.10 ≤ x ≤ 0.20) ceramics consist of the pyrochlore-type structure and a small amount of CaZrO₃. The total conductivity of GdSm_1?xCa_xZr₂O_7?x/2 ceramics follows the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm_1?xCa_xZr₂O_7?x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10^?4–1.0 atm at each test temperature. The highest total conductivity is about 1.20 × 10^?2 S cm^?1 at 1173 K for the GdSm_0.9Ca_0.1Zr₂O_6.95 ceramic.     

Thermophysical properties of Yb2O3 doped Gd2Zr2O7 and thermal cycling durability of (Gd0.9Yb0.1)2Zr2O7/YSZ thermal barrier coatings

(Gd_1−xYb_x)₂Zr₂O₇ compounds were synthesized by solid reaction. Yb₂O₃ doped Gd₂Zr₂O₇ exhibited lower thermal conductivities and higher thermal expansion coefficients (TECs) than Gd₂Zr₂O₇. The TECs of (Gd_1−xYb_x)₂Zr₂O₇ ceramics increased with increasing Yb₂O₃ contents. (Gd_0.9Yb_0.1)₂Zr₂O₇ (GYbZ) ceramic exhibited the lowest thermal conductivity among all the ceramics studied, within the range of 0.8–1.1 W/mK (20–1600 °C). The Young's modulus of GYbZ bulk is 265.6 ± 11 GPa. GYbZ/YSZ double-ceramic-layer thermal barrier coatings (TBCs) were prepared by electron beam physical vapor deposition (EB-PVD). The coatings had an average life of more than 3700 cycles during flame shock test with a coating surface temperature of ∼1350 °C. Spallation failure of the TBC occurred by delamination cracking within GYbZ layer, which was a result of high temperature gradient in the GYbZ layer and low fracture toughness of GYbZ material.     

Marked reduction in the thermal conductivity of (La0.2Gd0.2Y0.2Yb0.2Er0.2)2Zr2O7 high-entropy ceramics by substituting Zr4+ with Ti4+

The (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ (x = 0–0.5) high-entropy ceramics were successfully prepared by a solid state reaction method and their structures and thermo-physical properties were investigated. It was found that the high-entropy ceramics demonstrate pure pyrochlore phase with the composition of x = 0.1–0.5, while (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂Zr₂O₇ shows the defective fluorite structure. The sintered high-entropy ceramics are dense and the grain boundaries are clean. The grain size of high-entropy ceramics increases with the Ti⁴⁺ content. The average thermal expansion coefficients of the (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics range from 10.65 × 10^?6 K^?1 to 10.84 × 10^?6 K^?1. Importantly, the substitution of Zr⁴⁺ with Ti⁴⁺ resulted in a remarkable decrease in thermal conductivity of (La_0.2Gd_0.2Y_0.2Yb_0.2Er_0.2)₂(Zr_1-xTi_x)₂O₇ high-entropy ceramics. It reduced from 1.66 W m^?1 K^?1 to 1.20 W m^?1 K^?1, which should be ascribed to the synergistic effects of mass disorder, size disorder, mixed configuration entropy value and rattlers.     

Phase evolution,microstructure and chemical stability of Ca1-xZr1-xGd2xTi2O7 (0.0 ≤ x ≤ 1.0) system for immobilizing nuclear waste

In order to ascertain the structural relationship of zirconolite and pyrochlore for their potential application in HLW immobilization, the Gd-doped zirconolite-pyrochlore composite ceramics (Ca_1-xZr_1-xGd_2xTi₂O₇) were systematically synthesized with x?=?0.0–1.0 by traditional solid-phase reaction method. The phase evolution and microstructure of the as-prepared samples have been elucidated by XRD and Rietveld refinement, Raman spectroscopy, BSE-EDS and HRTEM analysis. The results showed that zirconolite-2M, zirconolite-4M, perovskite and pyrochlore, four phases were identified in Ca_1-xZr_1-xGd_2xTi₂O₇ system and could be coexisted at x?=?0.4 composition. With the increase of Gd³⁺ substitution, the phase evolution was followed by zirconolite-2M→zirconolite-4M→pyrochlore. It is illustrated that the phase transformation from zirconolite-2M to zirconolite-4M was promoted by the preferential substitution of Gd³⁺ for Ca²⁺. And the solubility of Gd³⁺ in zirconolite-2M, zirconolite-4M and pyrochlore increased in sequence. The chemical stability test was also measured by the PCT leaching method. The normalized elemental release rates of Ca, Zr, Ti and Gd in Ca_1-xZr_1-xGd_2xTi₂O₇ system were fairly low and in the range of 10^?6?10^?8 g?m^?2 d^?1, which indicated a potential ceramics composite ensemble of CaZrTi₂O₇-Gd₂Ti₂O₇ system for nuclear HLW immobilization.     

The structure and electrical properties of lithium doped pyrochlore Gd2Zr2O7

The lithium-doped phases Gd_1.7Li_0.3Zr₂O_6.7 and Gd₂Zr_1.7Li_0.3O_6.55 with a pyrochlore structure were prepared by the modified Pechini method using citric acid and glycerol. Monitoring of the lithium content by using a nuclear microanalysis showed that a significant loss of lithium occurred after heat treatment above 1200 °C. Dense ceramics with a stoichiometric lithium content can be prepared by a low temperature microwave sintering (1100 °C). The introduction of lithium in the Gd-sublattice was accompanied by a decrease in the unit cell parameter (a = 10.5208 (1) Å vs 10.5346 (2) Å for Gd₂Zr₂O₇) and during doping at the Zr-sites with lithium, the cell parameter increased (10.5720 (1) Å). The doping in both cases led to an increase in the free cell volume. The impedance spectroscopy results showed that the bulk conductivity can be enhanced by the Li⁺-doping at the Gd³⁺-site by almost an order of magnitude. The sample Gd₂Zr_1.7Li_0.3O_6.55 had a conductivity lower than that of Gd_1.7Li_0.3Zr₂O_6.7 due to the possible trapping of oxygen vacancies by a high-charged acceptor defect LiZr???. The conductivity?pO₂ measurements showed that the Li-containing phase was a pure oxide-ion conductor at T < 800 °C.     

Densifications and mechanical properties of single-phase Gd2Zr2O7 ceramic waste forms with improved TRPO waste load

A nitrate–citrate combustion method combined with microwave sintering was firstly employed for the rapid fabrication of the Gd₂Zr₂O₇ matrix immobilizing various amounts of simulated nuclear wastes. Phase evolutions, microstructure changes, element distributions, densification processes and mechanical properties of the as-prepared (1 – x)Gd₂Zr₂O₇·xTRPO (0.0 ≤ x ≤ 0.6) at various temperatures were investigated. Compared to the reported studies, we have increased the immobilization amount of simulated TRPO waste within a crystal structure from 45 to 60 wt%. T_d and T_g (the threshold temperatures to trigger accelerated densification and grain growth, respectively) were employed to divide the densification process into three stages. the mechanical properties and the densification stages of the (1 – x)Gd₂Zr₂O₇·xTRPO (0.0 ≤ x ≤ 0.6) ceramics sintered under microwave sintering at various temperatures were finally determined. Fine-grained (1 – x)Gd₂Zr₂O₇·xTRPO (0.0 ≤ x ≤ 0.6) ceramic waste forms with average grain size less than 200 nm and relative density higher than 90% can be obtained by microwave sintering at sintering temperature less than 1400 °C.     

Influence of TiO2 doping on thermo-optical properties of pyrochlore Sm2(Zr1–xTix)2O7 (0≤x≤0.15) ceramics

Sm₂(Zr_1–xTi_x)₂O₇ (0≤x≤0.15) ceramics have been fabricated by pressureless-sintering method at 1973 K for 10 h in air. The influence of TiO₂ doping on microstructure and thermo-optical properties of Sm₂(Zr_1–xTi_x)₂O₇ ceramics is investigated by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy measurements. The partial substitution of Ti⁴⁺ for Zr⁴⁺ results in a significant increase in emissivity at low wavelengths contrasted with undoped Sm₂Zr₂O₇. Sm₂(Zr_0.85Ti_0.15)₂O₇ ceramic exhibits a high emissivity of above 0.70 at 1073 K in a wavelength range of 3–16 µm, where the highest value at this temperature is more than 0.90 especially in the wavelength range of 9–14 µm. FT-IR spectra and optical absorption spectra unveil the mechanisms of enhanced emissivity in Sm₂(Zr_1–xTi_x)₂O₇ (0.05≤x≤0.15) ceramics in the intermediate infrared range, especially at the wavelengths of 3–8 µm, due to Ti⁴⁺ ion substitution for Zr⁴⁺ ion.     

Volcanic Ash‐Induced Decomposition of EB‐PVD Gd2Zr2O7 Thermal Barrier Coatings to Gd‐Oxyapatite,Zircon, and Gd,Fe‐Zirconolite

The resistance of EB‐PVD Gd₂Zr₂O₇ thermal barrier coatings against high‐temperature infiltration and subsequent degradation by molten volcanic ash is investigated by microstructural analysis. At 1200°C, EB‐PVD Gd₂Zr₂O₇ coatings with silica‐rich, artificial volcanic ash (AVA) overlay show a highly dynamic and complex recession scenario. Gd₂O₃ is leached out from Gd₂Zr₂O₇ by AVA and rapidly crystallizes as an oxyapatite‐type solid‐solution (Ca,Gd)₂(Gd,Zr)₈(Si,Al)₆O₂₆. The second product of Gd₂Zr₂O₇ decomposition is Gd₂O₃ fully stabilized ZrO₂ (Gd‐FSZ). Both reaction products are forming an interpenetrating network filling open coating porosity. However, first‐generation Gd‐oxyapatite and Gd‐FSZ are exhibiting chemical evolution in the long term. The chemical composition of Gd‐oxyapatite does evolve from Ca,Zr enriched to Gd‐rich. AVA continuously leaches out Gd₂O₃ from Gd‐FSZ followed by destabilization to the monoclinic ZrO₂ polymorph. Finally, zircon (ZrSiO₄) is formed. In addition to the prevalent formation of Gd‐oxyapatite, a Gd‐, Zr‐, Fe‐, and Ti‐rich oxide is observed. From chemical analysis and electron diffraction it is concluded that this phase belongs to the zirconolite‐type family (zirconolite CaZrTi₂O₇), exhibiting an almost full substitution Ca²⁺ + Ti⁴⁺ <> Gd³⁺ + Fe³⁺. As all Gd₂Zr₂O₇ decomposition products with the exception of ZrSiO₄ exhibit considerable solid solubility ranges, it is difficult to conclusively assess the resistance of EB‐PVD Gd₂Zr₂O₇ coatings versus volcanic ash attack.     

High capacity crystal immobilization of U5+ and U6+ by ZrSiO4 ceramics

ZrSiO₄-based ceramics have been considered as one of the candidate nuclear waste forms, while the immobilization behavior of mixed-valent uranium in the structure of the ceramics was unclear. Herein, ZrSiO₄–U ceramics with a general formula of Zr_1-4x(U⁶⁺_xU⁵⁺_2x)SiO₄ were designed and synthesized. The evolutions of phase and microstructure depending on the content of U were investigated. The ceramics with 0 ≤ x < 0.04 showed a single ZrSiO₄ phase, while U₃O₈ phase was detected when x ≥ 0.04. The results demonstrated that the solubility limit of U in ZrSiO₄ ceramic was up to 1.51 at.% or 11.06 wt%. The calculated lattice parameters increased with the increase of U content. The increased parameters provided the evidence of the immobilization of both U⁵⁺ and U⁶⁺ into ZrSiO₄ crystal lattice by replacing Zr⁴⁺. Furthermore, the obtained ZrSiO₄–U ceramics exhibited good aqueous durability (∼10⁻⁵ g m⁻² d⁻¹). The results indicated that ZrSiO₄-based ceramics can be employed to effectively immobilize mixed-valent U.     

Influence of doping Mg2+ or Ti4+ captions on the microstructures,thermal radiation and thermal cycling behavior of plasma-sprayed Gd2Zr2O7 coatings

Gadolinium zirconate (Gd₂Zr₂O₇) coatings doped by the transition metal Ti and the alkaline earth metal Mg were expected to have improved thermal radiation performance, which could be combined with their excellent thermal barrier properties to comprehensively improve the thermal insulating performance. The results show that the parent Gd₂Zr₂O₇ powder as well as the Gd-site and Zr-site substituted powders crystallize as pyrochlore Gd₂Zr₂O₇ in Fd-3m space group, while all the as-sprayed coatings have the combination of fluorite and a little part of pyrochlore phase. Gd₂Zr₂O₇ ceramic has high mid-infrared emittance and the addition of Ti⁴⁺ into Gd₂Zr₂O₇ can enhance the infrared absorption/emittance in a specific wavenumber range, dominantly in the near-infrared (0.75–2.5 μm) band due to the enhancement of electron transition induced by the impurity energy levels linked to the widening of the conduction band. The normal spectral infrared emissivity of Gd₂Zr₂O₇-based coating was higher than 0.88 at 1073 K. The monolayered doped Gd₂Zr₂O₇ coatings present very low thermal cycling lifetime, similar with the parent coating, mainly related with their low fracture toughness, despite (Gd_1-xMg_x)₂Zr₂O₇ series display lower thermal conductivity than the parent one.     

Titanium substitution in Gd2Zr2O7 for thermal barrier coating applications

The study underlines the impact of Ti⁴⁺ substitution in Gd₂Zr₂O₇ for applications in thermal barrier coatings (TBC). Depending on the Ti⁴⁺ content, two different crystal structures of Gd₂Zr₂O₇ namely pyrochlore and fluorite were determined. Ti⁴⁺ substitutions in the increasing order induced a gradual contraction of Gd₂Zr₂O₇ unit cell; however, with the accomplishment of concentration dependent crystal structures of either single phase pyrochlore or mixtures of pyrochlore and fluorite. Absorption measurements enunciated the enhanced infra-red reflectance behaviour of Gd₂Zr₂O₇ due to Ti⁴⁺ substitutions. A gradual increment in the concentration of Ti⁴⁺ substitutions in Gd₂Zr₂O₇ envisaged a simultaneous porous to dense morphological features, which reflected in the resultant mechanical data. Hot corrosion studies ensure the critical role of Ti⁴⁺ to retain the crystal structure of Gd₂Zr₂O₇.     

Fabrication and characterization of novel excellent thermal-protection Gd2Zr2O7/ZrO2 composite ceramic fibers with different proportions of Gd2Zr2O7

Three kinds of Gd₂Zr₂O₇/ZrO₂ (GZC) composite fibers with different proportions of Gd₂Zr₂O₇ were prepared by electrospinning method through changing the amount of Gd³⁺ in precursor solutions. The thermal decomposition, crystallization process, high temperature stability and heat-conducting properties of GZC fibers were fully characterized. The results showed that there were three crystalline phases, tetragonal phase ZrO₂, cubic phase ZrO₂ and defect fluorite phase Gd₂Zr₂O₇ in all the GZC fibers. The content of Gd₂Zr₂O₇ increased gradually with the increase of Gd³⁺ in precursor solutions which led to the gradual slowing down of grain growth rate, the decrease of thermal conductivity and the increase of high temperature stability of the obtained composite fibers. The thermal conductivities of all the GZC fiber sheets were lower than that of 7YSZ fiber sheet. The sheets of all the GZC fibers could keep the high temperature stability up to 1300 °C.     

Alpha-particle irradiation effects on uranium-bearing Gd2Zr2O7 ceramics for nuclear waste forms

It is necessary to study the self-irradiation effects of nuclear waste forms under α-decay in the long term storage. In the present work, accelerated irradiation experiments were performed on (Gd_1-4xU_2x)₂(Zr_1-xU_x)₂O₇ (x = 0, 0.10, 0.14) samples using 0.5 MeV alpha-particle irradiation at fluences ranging from 1 × 10¹⁴ to 1 × 10¹⁷ ions/cm² at room temperature. Irradiation induced microstructural evolution was examined by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and Field-emission scanning electron microscopy (FESEM). The results show that the main crystal structure is kept, however, weaker structural ordering is leaded as a result of intensified irradiation. And the radiation resistance is enhanced by the growing uranium content in the discussed range. Moreover, the irradiation effects as a function of depth have been discussed. Raman spectra reveal that the vibration intensity of atomic bonds are changed due to increased irradiation. In addition, the microtopography and element distribution have been kept after irradiation.     

Expanding negative thermal expansion range of ZrMnMo3O12 to cover room temperature by introducing V5+

Solid solutions of Zr_1+xMn_1-xMo_3-2xV_2xO₁₂ (0 ≤ x ≤ 0.5) are developed with reduced phase transition temperature (from 362 to 160 K) by introducing V⁵⁺ into ZrMnMo₃O₁₂. Zr_1+xMn_1-xMo_3-2xV_2xO₁₂ adopt monoclinic (P2₁/a) and orthorhombic (Pbcn) structure at room temperature (RT) for x ≤ 0.1 and x ≥ 0.2, respectively. The formation of bond V–O induces a larger average effective negative charge on oxygen to enhance the repulsive force between them and then strengthens the bond of Mo–O, which reduces the phase transition temperature due to the reduction in effective electronegativity and expands negative thermal expansion (NTE) range covering RT. NTE property in a wide temperature range (from 160 to 673 K) for Zr_1.5Mn_0.5Mo₂VO₁₂ is realized, implying great potential for applications. The NTE property of the materials is induced by low-frequency phonons.