Na2TiGeO5: Crystal structure stability at low temperature and high pressure

A. Waskowska, Leif Gerward, J.S. Olsen, A. Sieradzki, W. Morgenroth

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyramids and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K suggest that {110} domains, developing below T-c, entail a tetragonal-to-orthorhombic symmetry change. The mechanism is attributed to a shortening of the O-O distance between the polyhedral layers, and to minor shifts of the positions of the Ti atoms and the correlated oxygen atoms along the c-axis. The structure distortion, however, is too small to allow any unambiguous determination of the symmetry-breaking effects. The bulk modulus and its pressure derivative have been determined as B-0 = 89(2) GPa and B'(0) = 4.0. A pressure-induced phase transformation takes place at P-c approximate to 12.5 GPa, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa.
Original languageEnglish
JournalJournal of Physics and Chemistry of Solids
Volume69
Issue number4
Pages (from-to)815-821
ISSN0022-3697
DOIs
Publication statusPublished - 2008

Keywords

  • phase transition
  • oxides
  • X-ray diffraction
  • thermal expansion

Cite this

Waskowska, A. ; Gerward, Leif ; Olsen, J.S. ; Sieradzki, A. ; Morgenroth, W. / Na2TiGeO5: Crystal structure stability at low temperature and high pressure. In: Journal of Physics and Chemistry of Solids. 2008 ; Vol. 69, No. 4. pp. 815-821.
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abstract = "The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyramids and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K suggest that {110} domains, developing below T-c, entail a tetragonal-to-orthorhombic symmetry change. The mechanism is attributed to a shortening of the O-O distance between the polyhedral layers, and to minor shifts of the positions of the Ti atoms and the correlated oxygen atoms along the c-axis. The structure distortion, however, is too small to allow any unambiguous determination of the symmetry-breaking effects. The bulk modulus and its pressure derivative have been determined as B-0 = 89(2) GPa and B'(0) = 4.0. A pressure-induced phase transformation takes place at P-c approximate to 12.5 GPa, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa.",
keywords = "phase transition, oxides, X-ray diffraction, thermal expansion",
author = "A. Waskowska and Leif Gerward and J.S. Olsen and A. Sieradzki and W. Morgenroth",
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Waskowska, A, Gerward, L, Olsen, JS, Sieradzki, A & Morgenroth, W 2008, 'Na2TiGeO5: Crystal structure stability at low temperature and high pressure', Journal of Physics and Chemistry of Solids, vol. 69, no. 4, pp. 815-821. https://doi.org/10.1016/j.jpcs.2007.09.011

Na2TiGeO5: Crystal structure stability at low temperature and high pressure. / Waskowska, A.; Gerward, Leif; Olsen, J.S.; Sieradzki, A.; Morgenroth, W.

In: Journal of Physics and Chemistry of Solids, Vol. 69, No. 4, 2008, p. 815-821.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Na2TiGeO5: Crystal structure stability at low temperature and high pressure

AU - Waskowska, A.

AU - Gerward, Leif

AU - Olsen, J.S.

AU - Sieradzki, A.

AU - Morgenroth, W.

PY - 2008

Y1 - 2008

N2 - The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyramids and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K suggest that {110} domains, developing below T-c, entail a tetragonal-to-orthorhombic symmetry change. The mechanism is attributed to a shortening of the O-O distance between the polyhedral layers, and to minor shifts of the positions of the Ti atoms and the correlated oxygen atoms along the c-axis. The structure distortion, however, is too small to allow any unambiguous determination of the symmetry-breaking effects. The bulk modulus and its pressure derivative have been determined as B-0 = 89(2) GPa and B'(0) = 4.0. A pressure-induced phase transformation takes place at P-c approximate to 12.5 GPa, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa.

AB - The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyramids and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K suggest that {110} domains, developing below T-c, entail a tetragonal-to-orthorhombic symmetry change. The mechanism is attributed to a shortening of the O-O distance between the polyhedral layers, and to minor shifts of the positions of the Ti atoms and the correlated oxygen atoms along the c-axis. The structure distortion, however, is too small to allow any unambiguous determination of the symmetry-breaking effects. The bulk modulus and its pressure derivative have been determined as B-0 = 89(2) GPa and B'(0) = 4.0. A pressure-induced phase transformation takes place at P-c approximate to 12.5 GPa, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa.

KW - phase transition

KW - oxides

KW - X-ray diffraction

KW - thermal expansion

U2 - 10.1016/j.jpcs.2007.09.011

DO - 10.1016/j.jpcs.2007.09.011

M3 - Journal article

VL - 69

SP - 815

EP - 821

JO - Journal of Physics and Chemistry of Solids

JF - Journal of Physics and Chemistry of Solids

SN - 0022-3697

IS - 4

ER -