First Evidence of a Phase Transition in a High-Pressure Metal Iodate: Structural and Thermal Studies of AgIO3 Polymorphs

• Published in: European journal of inorganic chemistry Vol. 2013; no. 20; pp. 3526 - 3532
• Main Authors: Suffren, Yan, Gautier-Luneau, Isabelle, Darie, Céline, Goujon, Céline, Legendre, Murielle, Leynaud, Olivier
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Subjects: Chemical Sciences; Cristallography; High-pressure chemistry; Inorganic chemistry; Iodates; Material chemistry; Phase transitions; Structure elucidation; Iodates; Phase transitions; Structure elucidation; High-pressure chemistry
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201300191

A new phase of silver iodate, β‐AgIO3, was obtained at 2.7 GPa by heating the α‐AgIO3 precursor above 240 °C. β‐AgIO3 is the first iodate obtained at high pressure that stabilizes under normal conditions. The crystal structure was determined by X‐ray powder diffraction and Rietveld refinement. In comparison to α‐AgIO3, which crystallizes in the Pbc21 acentric orthorhombic space group with the lattice parameters a = 7.265(2) Å, b = 15.17(4) Å, c = 5.786(2) Å, and V = 638(2) Å3, β‐AgIO3 crystallizes in the Pbca centric orthorhombic space group, with the following parameters: a = 6.137(2) Å, b = 16.980(4) Å, c = 5.827(1) Å, and V = 607.3(3) Å3. Differential thermal analysis under high pressure (2.7 GPa) and structural studies showed an endothermic transformation at 260 °C corresponding to a first‐order reconstructive phase transition from α‐AgIO3 to β‐AgIO3. The thermal behaviors of α‐AgIO3 and β‐AgIO3 were studied by differential scanning calorimetry at ambient pressure and in situ temperature‐dependent X‐ray powder diffraction. β‐AgIO3 is the first iodate phase obtained under high pressure. The reconstructive phase transition from the α‐AgIO3 acentric phase to the dense β‐AgIO3 centric phase is an endothermic transformation that occurs at 260 °C at 2.7 GPa.