Structures and negative thermal expansion properties of solid solutions Y Nd2−W3O12 (x= 0.0–1.0, 1.6–2.0)

Two Decades of Negative Thermal Expansion Research: Where Do We Stand?

“…Ln 2 M 3 O 12 compositions with larger lanthanides crystallize in structures that adopt higher coordination numbers (7 or 8) for the A-site. However, for solid solutions of two trivalent cations, significant amounts of larger Ln 3+ can be incorporated into the scandium tungstate structure, as evidenced by reports of Er 2−x Ce x W 3 O 12 (x ≤ 0.4) [118], Er 2−x Sm x W 3 O 12 (x ≤ 0.5) [119], Er 2−x Nd x W 3 O 12 (x ≤ 0.5) [120], Er 2−x Dy x W 3 O 12 (x ≤ 0.7) [121], Y 2−x Dy x W 3 O 12 (x ≤ 1.0) [121], and Y 2−x Nd x W 3 O 12 (x ≤ 0.4) [122]. In addition, substitution with aliovalent cations has been achieved in AP 2 MO 12 [123,124] and MgAM 3 O 12 (A = Zr, Hf; M = Mo, W) [125,126,127].…”

“…As a result, expansion tends to become more negative with increasing size of A 3+ , reaching values of −7.0 × 10 −6 K −1 in Y 2 W 3 O 12 [129] and −9.3 × 10 −6 K −1 in Y 2 Mo 3 O 12 . Additional slight decreases have been achieved in solid solutions of these compounds with larger lanthanides [118,119,120,121,122]. In contrast, Al 2 W 3 O 12 has been reported to show low positive expansion with an α l value of +2.2 × 10 −6 K −1 [5].…”

“…Under ambient conditions, a trihydrate is formed by absorption of moisture from the atmosphere [118,119,120,121,122,131,132]. This limits the usefulness of these compositions to temperatures above the dehydration point or sealed systems.…”

Tuning the monoclinic-to-orthorhombic phase transition temperature of Fe2Mo3O12by substitutional co-incorporation of Zr4+and Mg2+

“…The b-axis shows expansion from 300 to 500 K and contraction from 500 to 1000 K. The phenomenon may be the result from lattice distortion by substitution of (ZrMg) 61 for Fe 31 . 28 The replacement has more impact on the b-axis than a-and c-axis. The average axial CTEs from 300 to 1000 K are calculated to be a a 5 7.64 Â 10 À6 K À1 , a b 5 À0.20 Â 10 À6 K À1 , a c 5 À1.38 Â 10 À6 K À1 for Fe 0.4 (ZrMg) 0.8 Mo 3 O 12 and a a 5 7.50 Â 10 À6 K À1 , a b 5 À0.50 Â 10 À6 K À1 , a c 5 À2.05 Â 10 À6 K À1 for Fe 0.2 (ZrMg) 0.9 Mo 3 O 12 .…”

The crystal structure and thermal expansion properties of solid solutions Ln2−xDyxW3O12 (Ln=Er and Y)

“…Hu). structure and thermal expansion properties of solid solutions forming from mixing the orthorhombic compound and monoclinic compound [12]. For example, we have previously reported our work on solid solutions of Er 2−x B x W 3 O 12 (B = Sm, Nd and Ce) [13][14][15].…”