Buysser Klaartje De, Driessche Isabel Van, Putte Bart Vande, Vanhee Paul, Schaubroeck Joseph, Hoste Serge
Department of Inorganic and Physical Chemistry, Building S3 Ghent University Krijgslaan 281, 9000 Ghent, Belgium.
Inorg Chem. 2008 Jan 21;47(2):736-41. doi: 10.1021/ic701660w. Epub 2007 Dec 21.
The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.
负热膨胀材料ZrW₂O₈已知会经历有序-无序相变，这会影响其膨胀行为。在本研究中，研究了Ti⁴⁺和Sn⁴⁺作为ZrW₂O₈中Zr⁴⁺位置可能的替代离子。这种替代导致晶胞参数减小，因为取代基的离子半径小于Zr⁴⁺的离子半径。注意到转变温度有显著降低。使用差示扫描量热法（DSC）来量化相变过程中的焓变和熵变，以揭示这种降低背后的机制。结果表明，M-O键的强度起着重要作用，因为它是刚性单元模式运动和有序-无序转变机制中的一个因素。
