Negative and zero thermal expansion in α-(Cu_2-Zn)V₂O₇ solid solutions.

Area of Science:

• Materials Science
• Solid State Chemistry

Background:

• Negative or zero thermal expansion (NTE/ZTE) is crucial for advanced materials with precise dimensional stability.
• Controlling thermal expansion is essential for applications in electronics and aerospace.

Purpose of the Study:

• To investigate the effect of zinc substitution on the thermal expansion properties of orthorhombic α-Cu2V2O7.
• To tune the volumetric coefficients of thermal expansion (CTE) from negative to zero values.

Main Methods:

• Synthesis of a series of orthorhombic α-Cu2-xZnxV2O7 (x = 0, 0.1, 0.2) compounds.
• Characterization of crystal structure and thermal expansion behavior using X-ray diffraction and dilatometry.
• Analysis of vibrational modes contributing to thermal expansion.

Main Results:

• Volumetric coefficients of thermal expansion were successfully tuned from -10.19 × 10-6 K-1 to -1.58 × 10-6 K-1 between 100-475 K.
• Transverse vibrations of oxygen-vanadium bonds were identified as the primary cause of NTE in α-Cu2V2O7.
• Zinc incorporation led to crystal structure densification, suppressing vibrations and achieving ZTE in α-Cu1.8Zn0.2V2O7.

Conclusions:

• Zinc substitution is an effective strategy to control and achieve zero thermal expansion in anisotropic framework materials.
• Understanding the role of lattice vibrations is key to designing materials with tailored thermal expansion properties.