Pre-transitional behavior in cubic potassium niobate

M. Holma*, H. Hong, M. Nelson, H. D. Chen

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

Pre-transitional behavior prior to the onset of the cubic-to-tetragonal phase transformation in KNbO3 has been studied with synchrotron x-ray scattering at NSLS, Brookhaven National Lab. Measurements of the Thermal Diffuse Scattering (TDS), Grazing Incidence X-ray Scattering (GIXS), and precursor Bragg scattering have been performed at a series of temperatures on a single crystal sample in the cubic phase (Tc = 405 °C). The TDS was measured in the (001), (011) and (111) cubic planes. The GIXS was measured above, at and below the critical scattering angle of the sample. Based on localized soft mode theory, dynamic tetragonal fluctuations may be expected prior to the onset of the phase transition initiated by defects or surfaces. The GIXS data indicate that the tetragonal phase is apparent prior to the phase transition of the bulk -- consistent with the notion that nucleation originates from potent defect sites during a martensitic-like displacive transformation. The TDS intensity distribution is disk-shaped; arising from a localized, low energy transverse optic mode in the [100] directions extending out to the Brillouin zone boundary (reduced wave vector, q = 0.5). Scans made in the (011) planes show TDS intensity extending out to a reduced wave vector of q - 0.2. Preliminary analysis indicates that a low energy transverse optic mode extends in the [011] direction as well. The TDS intensity decreases as the transition temperature is approached from above. Comparison of the TDS results with inelastic neutron scattering data will be made.

Original languageEnglish
Title of host publicationApplications of Synchrotron Radiation Techniques to Materials Science
PublisherPubl by Materials Research Society
Pages293-298
Number of pages6
ISBN (Print)1558992030
DOIs
StatePublished - 1 Jan 1993
EventMaterials Research Society Spring Meeting - San Francisco, CA, USA
Duration: 12 Apr 199315 Apr 1993

Publication series

NameMaterials Research Society Symposium Proceedings
Volume307
ISSN (Print)0272-9172

Conference

ConferenceMaterials Research Society Spring Meeting
CitySan Francisco, CA, USA
Period12/04/9315/04/93

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