Phase transitions in KIO3

• Published in: Journal of physics. Condensed matter Vol. 24; no. 32
• Main Authors: Bayarjargal, Lkhamsuren, Wiehl, Leonore, Friedrich, Alexandra, Winkler, Björn, Juarez-Arellano, Erick A, Morgenroth, Wolfgang, Haussühl, Eiken
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 15.08.2012; Institute of Physics
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Physics; Solid-solid transitions; Specific phase transitions; Second harmonic generation; Raman spectra; Pressure effects; Phase transformations; XRD; Potassium Iodates; High pressure; Monocrystals; Equations of state; Shear stress; Density functional method; Bulk modulus; Synchrotron radiation; Crystal structure
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/24/32/325401

The high-pressure behavior of KIO3 was studied up to 30 GPa using single crystal and powder x-ray diffraction, Raman spectroscopy, second harmonic generation (SHG) experiments and density functional theory (DFT)-based calculations. Triclinic KIO3 shows two pressure-induced structural phase transitions at 7 GPa and at 14 GPa. Single crystal x-ray diffraction at 8.7(1) GPa was employed to solve the structure of the first high-pressure phase (space group R3, a = 5.89(1) , α = 62.4(1)°). The bulk modulus, B, of this phase was obtained by fitting a second order Birch-Murnaghan equation of state (eos) to synchrotron x-ray powder diffraction data resulting in Bexp,second = 67(3) GPa. The DFT model gave BDFT,second = 70.9 GPa, and, for a third order Birch-Murnaghan eos, BDFT,third = 67.9 GPa with a pressure derivative of . Both high-pressure transformations were detectable by Raman spectroscopy and the observation of second harmonic signals. The presence of strong SHG signals shows that all high-pressure phases are acentric. By using different pressure media, we showed that the transition pressures are very strongly influenced by shear stresses. Earlier work on low- and high-temperature transitions was complemented by low-temperature heat capacity measurements. We found no evidence for the presence of an orientational glass, in contrast to earlier dielectric studies, but consistent with earlier low-temperature diffraction studies.