Orientational order-dependent thermal expansion and compressibility of ZrW2O8 and ZrMo2O8

Abstract

The role of MO4 (M = W, Mo) orientational disorder in the thermal expansion and compressibility of ZrW2O8 and ZrMo2O8 was investigated via in situ powder X-ray diffraction at elevated temperature and pressure. A dramatic reduction in the bulk modulus of α-ZrW2O8, which has ordered WO4 tetrahedra at room temperature, from 65 GPa at room temperature to 47 GPa at 386 K was observed to be concomitant with the onset of a reversible WO4 orientational disordering upon compression. Additionally, the coefficient of thermal expansion (CTE) of the α phase became more negative upon compression within the temperature range in which pressure-dependent disorder was observed; αl, over the range 298 to 386 K, was ~-11 ppm K(-1) at 35 MPa but ~-16 ppm K(-1) at 276 MPa. No softening upon heating or change in CTE upon compression was observed for ZrW2O8 above the order → disorder phase transition temperature. Cubic ZrMo2O8 has a disordered arrangement of MoO4 tetrahedra at all temperatures and pressures accessed in this study. Its bulk modulus was independent of temperature, and its CTE was insensitive to pressure, much like β-ZrW2O8. The stability/metastability of the cubic and orthorhombic phases upon heating above room temperature and compression is discussed, with a focus on changes in the thermodynamics and kinetics of the cubic ↔ orthorhombic transition.

Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

“…On compression to 1.38 GPa, ZrV 2 O 7 transforms to a phase with orthorhombic symmetry, and above 4 GPa it amorphizes [46,47]. The low temperature form of cubic ZrV 2 O 7 (κ T = 17 GPa) was reported to be much softer than other members of the ZrP 2 O 7 family at ambient temperature (κ T (ZrP 2 O 7 , TiP 2 O 7 ) ≃ 40 GPa) [46], and is much softer than previously studied ZrW 2 O 8 family members (κ T = 41-74 GPa) [14,15,34,48,49]. However, ZrV 2 O 7 only adopts a structure that supports NTE at above room temperature, and no high pressure studies have been performed on this phase.…”

“…However, thermal expansion mismatch between NTE and PTE materials in composites gives rise to internal stresses, which can be detrimental to the performance of the composite [9][10][11][12][13] as many NTE framework solids undergo phase transitions or changes in properties at low pressures. The combination of rich behavior upon modest compression and stresses arising from processing or thermal expansion mismatch motivates our studies of NTE materials under pressure [14][15][16][17][18][19][20][21][22][23][24].…”

Negative Thermal Expansion Near the Precipice of Structural Stability in Open Perovskites

“…Remarkably, there exists a growing class of materials with strong, isotropic, robust, and thermally persistent NTE that arises from structural motifs (Martinek and Hummel, 1968; Mary et al, 1996; Evans et al, 1997a,b; Pryde et al, 1997; Ernst et al, 1998; Perottoni and Jornada, 1998; Ramirez and Kowach, 1998; Ramirez et al, 2000; Mittal et al, 2001, 2004, 2018; Cao et al, 2002, 2003; Ouyang et al, 2002; Drymiotis et al, 2004; Hancock et al, 2004b; Kennedy and White, 2005; Lee et al, 2005; Tucker et al, 2005, 2007; Pantea et al, 2006; Figueirêdo and Perottoni, 2007; Han and Goddard, 2007; Keen et al, 2007, 2011; Schlesinger et al, 2008; Zhou et al, 2008; Greve et al, 2010; Gallington et al, 2013, 2014; Gupta et al, 2013; Morelock et al, 2013b; Bridges et al, 2014; Sanson, 2014). NTE in these systems is often discussed in connection with transverse fluctuations of a linkage between volume-defining vertices, which may accompany the librational, or hindered rotational motion of polyhedral subunits.…”

Synthesis, characterization, and functionalization of zirconium tungstate (ZrW2O8) nano‐rods for advanced polymer nanocomposites

“…Although they are widely used, epoxy resins come with some limitations, in particular their high coefficient of thermal expansion (CTE), which limits their suitability for aerospace and microelectronic applications . Zirconium tungstate (ZrW 2 O 8 )‐based nanomaterials have been used to develop low‐CTE polymer composites, and they are considered for more widespread applications .…”