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In 2 Mo 3 O 12 is considered to be a positive thermal expansion (PTE) material at room temperature since its negative thermal expansion (NTE) response temperature range is above 343 °C. With the expectation of tuning the NTE performance of In 2 Mo 3 O 12 , a series of In 2 Mo 3-x W x O 12 solid solutions was synthesized via B-site replacement by W6+. The effects of W6+ substitution on the phase composition, morphology, phase transition temperature (T pt) and thermal expansion behavior of In 2 Mo 3-x W x O 12 were systematically investigated. Results indicate that the replacement of Mo6+ by W6+ does not induce a change in the crystal structure of parent phase In 2 Mo 3 O 12 and can form continuous solid solutions of In 2 Mo 3-x W x O 12. With increasing composition parameter x, the T pt of In 2 Mo 3-x W x O 12 decreases, the corresponding NTE response temperature range is widened and NTE performance is improved. The coefficient of thermal expansion (CTE) of In 2 Mo 3-x W x O 12 becomes more negative. As expected, the T pt of In 2 Mo 3-x W x O 12 is tunable by adjusting the composition parameter x, and the tuning mechanism of NTE performance is discussed from the prospect of crystal structure. [ABSTRACT FROM AUTHOR]

Orthorhombic Sc 2 (MoO 4) 3 nanofibers have been prepared by ethylene glycol assisted electrospinning method. The effects of annealing temperature, precursor concentration, spinning distance and solvent on the preparation of Sc 2 (MoO 4) 3 nanofibers were characterized by XRD, SEM, HRTEM, EDX and high-temperature XRD. XRD analysis shows as-prepared nanofibers are amorphous. Orthorhombic Sc 2 (MoO 4) 3 nanofibers can be fabricated after annealing at different temperatures in 500–800 °C for 2 h. The crystallinity of Sc 2 (MoO 4) 3 nanofibers improves and the nanofiber diameter decreases gradually as the annealing temperature increases. However, the nanofiber structure was destroyed at the annealing temperature above 700 °C. Higher precursor concentration results in a slight increase of diameter and decrease in destroying temperature of Sc 2 (MoO 4) 3 nanofibers. Spinning distance also affects the diameter of nanofibers, and the nanofiber diameter decreases as the distance increases. One-dimensional orthorhombic Sc 2 (MoO 4) 3 nanofibers exhibit anisotropic negative thermal expansion. In 25–700 °C, the coefficients of thermal expansion (CTE) of α a , α b and α c are −5.81 × 10−6 °C−1, 4.80 × 10−6 °C−1 and -4.33 × 10−6 °C−1, and the α l of Sc 2 (MoO 4) 3 nanofibers is −1.83 × 10−6 °C−1. [ABSTRACT FROM AUTHOR]

In this work, Sc 2 Mo 3 O 12 has been synthesized via one-pot hydrothermal reaction. The effects of process conditions on the crystal structure, morphology, photocatalytic activity and negative thermal expansion (NTE) behaviors of flower-like Sc 2 Mo 3 O 12 were systematically investigated. Results indicate that orthorhombic flower-like Sc 2 Mo 3 O 12 assembled by nano-size flaky crystal grains can be synthesized by one-pot hydrothermal reaction at a temperature as low as 120 °C for 2 h. The hydrothermal reaction temperature and time have no obvious effects on the crystal structure and morphology. However, the photocatalytic property of synthesized Sc 2 Mo 3 O 12 is sensitive to the above parameters. The sample synthesized at 200 °C for 2 h shows the best photocatalytic degradation of methyl orange, and the degradation rate is 73.32% in 2 h 1The coefficient of thermal expansion (CTE) of Sc 2 Mo 3 O 12 is −1.99 × 10−6 °C−1 in 50–500 °C tested using TMA. The high-temperature XRD analysis reveals that Sc 2 Mo 3 O 12 exhibits anisotropic NTE and the intrinsic CTE is measured to be −2.09 × 10−6 °C−1 in 25–800 °C. [ABSTRACT FROM AUTHOR]

Orthorhombic Sc 2 Mo 3 O 12 films have been successfully prepared via spin coating technique followed by annealing at 500–750 °C. The phase composition, microstructure, morphology and negative thermal behavior of the synthesized Sc 2 Mo 3 O 12 films were investigated. XRD and XPS analysis indicate that as-deposited film is amorphous. Orthorhombic Sc 2 Mo 3 O 12 films can be prepared after post-annealing at 500–750 °C for 1 h. The crystallinity of Sc 2 Mo 3 O 12 films gradually improved with the increase of post-annealing temperature. SEM analysis shows as-deposited film is smooth and compact, and the grain size of Sc 2 Mo 3 O 12 film grows up as the post-annealing temperature increases. Variable temperature XRD analysis demonstrates that the synthesized orthorhombic Sc 2 Mo 3 O 12 films show stable thermo-chemical and anisotropic NTE property in 25–700 °C. The corresponding coefficients of thermal expansion (CTEs) of the orthorhombic Sc 2 Mo 3 O 12 film in a, b and c directions are −6.68 × 10−6 °C−1, 5.08 × 10−6 °C−1 and −4.76 × 10−6 °C−1, respectively. The whole unit cell of the orthorhombic Sc 2 Mo 3 O 12 film shrinks and the volumetric CTE of the Sc 2 Mo 3 O 12 thin film is −6.36 × 10−6 °C−1, and the linear CTE is about −2.12 × 10−6 °C−1 (α v = 3 α l). [ABSTRACT FROM AUTHOR]

A new series of cerium-substituted Y 2 W 3 O 12 ceramics were first fabricated with the goal of tailoring the thermal expansion and reducing the hygroscopicity. Influence of cerium substitution on the structure, hygroscopicity and thermal expansion property of Y 2 W 3 O 12 ceramics were investigated using XRD, FESEM, HRTEM, XPS, TGA and TMA. Results indicate that the Y 3+ can partly be substituted by Ce 3+ in Y 2- x Ce x W 3 O 12 ceramics and increasing substitution of Y 3+ in Y 2 W 3 O 12 by Ce 3+ results in the crystal structure change from orthorhombic to monoclinic. Single-phase Y 2- x Ce x W 3 O 12 ceramics can be synthesized in the range of 0.0 ≤ x ≤ 0.25 with an orthorhombic Y 2 W 3 O 12 -type crystal structure and 1.0 < x ≤ 2.0 with monoclinic Ce 2 W 3 O 12 -type crystal structure, respectively. As the amount of substituted cerium increases, the hygroscopic phenomenon of Y 2- x Ce x W 3 O 12 is significantly promoted, meanwhile the coefficient of thermal expansion gradually decreases. The linear coefficient of thermal expansion of Y 2- x Ce x W 3 O 12 ceramics can be adjusted from −13.094 × 10 −6  K −1 to 2.327 × 10 −6  K −1 by changing the substituted amount of cerium. Moreover, Y 0.25 Ce 1.75 W 3 O 12 does not absorb moisture in air and shows almost zero thermal expansion from 182 °C to 700 °C and its coefficient of thermal expansion is tested to be −0.820 × 10 −6  K −1 . This low thermal expansion Y 0.25 Ce 1.75 W 3 O 12 material may have great potential applications in manufacturing precision device in many fields. [ABSTRACT FROM AUTHOR]