Scientific article
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X-ray study on phase transitions of ferrolectric iron iodine boracite Fe3B7O13I at low temperatures

Published inPhysica status solidi. A, Applied research, vol. 10, p. 259-270
Publication date1972

The accurate lattice parameters of Fe I boracite, Fe3B7O13I, in the low-temp. range between -40 and -120 Deg were successfully detd. by using a special x-ray diffraction technique. To investigate the symmetry change occurring in this temp. range, Weissenberg diagrams were also studied. Ferroelec. Fe3B7O13I exhibits 2 kinds of monoclinic C2s and rhombohedral C36v phases, in addn. to the well-known orthorhombic C52v phase. The 2 kinds of monoclinic modifications, which are stable in the narrow temp. regions between the orthorhombic and rhombohedral phases, appear sep. depending on the history of temp. change of the crystal: one phase arises between -70 and -82 Deg with decreasing temp., the other between -55 and -68 Deg with increasing temp. They have almost similar crystal structures but possess slightly different lattice parameters, thermal expansion coeffs., and optical birefringences. The deviation of the axial angle b from 90 Deg in the monoclinic phases is less than half a minute. The deviation of the rhombohedral axial angle g is also extremely small; the difference from 60 Deg is 48 at -120 Deg. A simple model is proposed to explain the reason why the 2 monoclinic phases must bridge the orthorhombic and rhombohedral phases.

  • Phase transition iron iodine boracite
Affiliation Not a UNIGE publication
Citation (ISO format)
KOBAYASHI, Jinzo, SATO, Y., SCHMID, Hans. X-ray study on phase transitions of ferrolectric iron iodine boracite Fe<sub>3</sub>B<sub>7</sub>O<sub>13</sub>I at low temperatures. In: Physica status solidi. A, Applied research, 1972, vol. 10, p. 259–270.
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Article (Published version)
  • PID : unige:32039
ISSN of the journal0031-8965

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