Zero Thermal Expansion and Abrupt Amorphization on Compression in Anion Excess ReO₃-Type Cubic YbZrF₇

Abstract

Heat treatment of cubic YbZrF7, after quenching from 1000 °C, leads to a material displaying precisely zero thermal expansion at ∼300 K and negative thermal expansion at lower temperatures. The zero thermal expansion is associated with a minimum in the lattice constant at ∼300 K. X-ray total scattering measurements are consistent with a previously proposed model in which the incorporation of interstitial fluoride into the ReO3-related structure leads to both edge and corner sharing coordination polyhedra. The temperature dependence of the experimental pair correlation functions suggests that the expansions of edge and corner sharing links partly compensate for one another, supporting the hypothesis that the deliberate incorporation of excess fluoride into ReO3 structure materials can be used as a design strategy for controlling thermal expansion. Cubic YbZrF7 has a bulk modulus, K 0, of 55.4(7) GPa and displays pronounced pressure-induced softening [K 0′ = −27.7(6)] prior to an abrupt amorphization on compression above 0.95 GPa. The resulting glass shows a single sharp scattering maximum at Q ∼ 1.6 Å–1.

Perovskite-related ReO3-type structures

“…Examples include the parent compound, Sn 118,119 Pd, 120 Co, 121 Zn, 121 Mg, 122 Cu, 123 V, 124,125 Ti, 124 Ca, 119,126 Cr 119 ), M 2+ (Hf)F 6 compounds (where M = V, 124 Ti, 124 There are examples within those compounds which display NTE, 126,131,132 gas adsorption under pressure, 126 as well as Jahn-Teller distortions governed by the M 2+ character. 119,123,125 There are also the recent reports of the fluoride rich ReO 3 -type compound, YbZrF 7 , 133 which displays NTE below room temperature and ZTE at 300 K, and the Mg 1x Zr 1+x F 6+2x compounds in which the degree of thermal expansion can be tuned by varying x. 134 ReO 3 -type oxyfluorides, with general formula MO x F y (M = Ti, 135 V, 136 Ta, 137 Nb, 135,137 Zr, 138 Mo 139 ) are also known, with the first example reported in the 1950's.…”

Simultaneous Enhancement and Modulation of Upconversion by Thermal Stimulation in Sc2Mo3O12 Crystals

“…The thermal expansion of materials causes serious problems in practical applications. For example, even minute expansions can fatally degrade device performance in the semiconductor industry. − Nevertheless, a special set of crystalline materials are known to contract with an increase in temperature, due to the special arrangement of ions and particular vibration modes of the lattice. − The effect of negative thermal expansion (NTE) provides great opportunities for fine-tuning the thermal behavior of structural and functional materials. , By composing NTE materials with normal materials with positive coefficients of thermal expansion, one can construct zero thermal expansion materials for fiber optics and high-precision optical mirrors. − …”

High Pressure Behavior of Chromium and Yttrium Molybdate (Cr2Mo3O12, Y2Mo3O12)

“…Most materials get stiffer at high pressures due to reduction of empty space upon compression. However, pressure induced softening has been observed in a number of NTE material (Pantea et al, 2006; Fang and Dove, 2013, 2014; Fang et al, 2013; Morelock et al, 2013; Gallington et al, 2014; Hancock et al, 2015; Alabarse et al, 2017; Hester et al, 2017b; Ticknor et al, 2018), and has been linked to the facile polyhedral rotations that give rise to their expansion behavior. In many cases, amorphization is preceded by pressure induced softening as well.…”