Negative and zero thermal expansion in α-(Cu_2−xZn_x)V₂O₇ solid solutions

Abstract

Negative or zero thermal expansion (NTE, ZTE) of materials is intriguing for the controllable thermal expansion. We report a series of orthorhombic α-Cu2-xZnxV2O7 (x = 0, 0.1, 0.2), in which...

Strong Negative Thermal Expansion of Cu2PVO7 in a Wide Temperature Range

“…The thermal expansions of the “true” bond lengths of Cu–O and V–O measured by EXAFS are in both cases stronger than the “apparent” bond lengths extracted by SXRD. Such a difference can be observed in many NTE framework structured materials, like Cu 2 V 2 O 7 , ScF 3 , and many Prussian blue analogues. , It suggests that large transverse vibrations exist in Cu–O and V–O bonds. In addition, the similar V–O distances indicate the V sites in the same way for all V atoms with no preference of V 2 O 7 units.…”

“…However, the sintered ceramics prepared from different batches show different dilatometry results, and further research is under way. Such a strong NTE exceeds most of those of the NTE framework structure oxides, including NbVO 5 ( α v ∼ −6.63 × 10 –6 K –1 , 298–873 K), NbPO 5 ( α v ∼ −11 × 10 –6 K –1 , 673–973 K), α -Cu 2 V 2 O 7 ( α v ∼ −9.29 × 10 –6 K –1 , 100–573 K), , ThP 2 O 7 ( α v ∼ −10.5 × 10 –6 K –1 , 473–1174 K), Y 2 W 3 O 12 ( α v ∼ −20.9 × 10 –6 K –1 , 15–1373 K), and Sc 2 W 3 O 12 ( α v ∼ −6.67 × 10 –6 K –1 , 10–1200 K), and is even stronger than the average α v of ZrW 2 O 8 from 0.3 to 1050 K ( α v ∼ −21.9 × 10 –6 K –1 , 0.3–1050 K) . In 2019, Goodwin et al proposed the metrics of “NTE capacity”, denoted by χ α , to unbiasedly compare the NTE properties in different systems.…”

“…It seems not accurate to explain such a process by “rigid unit modes (RUMs)” which is a classical model to explain NTE in many framework structured materials, since there are deformations in both CuO 5 and P/VO 4 polyhedra. Actually, many framework structure oxides show NTE but without strict RUMs, such as ZrV 2 O 7 , Y 2 Mo 3 O 12 , Dy 2 W 3 O 12 , and α -Cu 2 V 2 O 7 . ,− Recently, reverse Monte Carlo analysis for neutron total scattering measurements of ScF 3 suggests the quasi-RUMs dominate the overall NTE . The NTE in those materials is also correlated with the rotation and twist among deformed polyhedra.…”

High-Temperature Zero Thermal Expansion in HfFe2+δ from Added Ferromagnetic Paths

“…9 In contrast, single-phase ZTE materials with good mechanical properties and homogeneous composition prevent the formation of cracks due to frequent temperature fluctuations. 4 Till date, only a few single-phase inorganic ZTE materials have been prepared, such as ferroelectric-based ZTE, 10,11 (Cu 2−x Zn x )-V 2 O 7 , 12 Zr 0.6 Sn 0.4 Mo 2 O 8 , 13 Sc 1.5 Al 0.5 W 3 O 12 , 14 and (Sc,M)F 3 (M = Ga, Fe). 15 Compared with inorganic materials, metal-based ZTE materials possess higher electron conductivity, higher thermal conductivity, and better mechanical performance.…”

“…In contrast, single-phase ZTE materials with good mechanical properties and homogeneous composition prevent the formation of cracks due to frequent temperature fluctuations . Till date, only a few single-phase inorganic ZTE materials have been prepared, such as ferroelectric-based ZTE, , (Cu 2– x Zn x )­V 2 O 7 , Zr 0.6 Sn 0.4 Mo 2 O 8 , Sc 1.5 Al 0.5 W 3 O 12 , and (Sc,M)­F 3 (M = Ga, Fe) …”