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dc.contributor.authorSmith, Rebecca Mary
dc.contributor.authorGardner, Jonathan
dc.contributor.authorMorrison, Finlay D.
dc.contributor.authorRowley, S. E.
dc.contributor.authorFerraz, Catarina
dc.contributor.authorCarpenter, M. A.
dc.contributor.authorChen, Jiasheng
dc.contributor.authorHodkinson, Jack
dc.contributor.authorDutton, Siân E.
dc.contributor.authorScott, James Floyd
dc.identifier.citationSmith , R M , Gardner , J , Morrison , F D , Rowley , S E , Ferraz , C , Carpenter , M A , Chen , J , Hodkinson , J , Dutton , S E & Scott , J F 2018 , ' Quantum critical points in ferroelectric relaxors : stuffed tungsten bronze K 3 Li 2 Ta 5 O 15 and lead pyrochlore (Pb 2 Nb 2 O 7 ) ' , Physical Review Materials , vol. 2 , no. 8 , 084409 .
dc.identifier.otherPURE: 255591835
dc.identifier.otherPURE UUID: 82dc7075-da10-4f16-8d18-21302eed72f7
dc.identifier.otherScopus: 85059609449
dc.identifier.otherORCID: /0000-0002-2813-3142/work/48131865
dc.identifier.otherWOS: 000442479200001
dc.identifier.otherORCID: /0000-0002-8862-8315/work/61133160
dc.description.abstractWe have synthesized ceramic specimens of the tetragonal tungsten bronze K3Li2Ta5O15 (KLT) and characterized its phase transition via X-ray diffraction, dielectric permittivity, resonant ultrasonic spectroscopy, and heat capacity measurements. The space group of KLT is reported as both P4/mbm and Cmmm with the orthorhombic distortion occurring when there are higher partial pressures of volatile K and Li used inside the closed crucibles for the solid state synthesis. The data show strong relaxor behavior, with the temperature at which the two dielectric relative permittivity peaks decreasing, with 104 ≥ Tm1 ≥ 69 K and 69 ≥ Tm2 ≥ 46 K as probe frequency f is reduced from 1 MHz to 316 Hz. F tests show that the data satisfies a Vogel-Fulcher model better than Arrhenius with an extrapolated freezing temperature for ε’ and ε” of Tf1 = +15.8 and –11.8 K and Tf2 = –5.0 and –15.0 K for f -> 0 (tending to dc). This difference between Tf from real and imaginary values, albeit counterintuitive, is mandatory, according to the theory of Tagantsev. Therefore, by tuning frequency, the transition could be shifted to absolute zero, suggesting KLT has a relaxor-type quantum critical point. In addition, we have reanalyzed the conflicting literature for Pb2Nb2O7 pyrochlore which suggests that this also has a relaxor-type quantum critical point since the freezing temperature from the Vogel-Fulcher fitting is below absolute zero. Since the transition temperature evidenced in the dielectric data at approximately 100 kHz shifts below 0 K for very low frequencies, this transition would not be seen with heat capacity data collected in the zero-frequency (dc) limit. Both of these materials show promise for possible new relaxor-type quantum critical points with non-perovskite based structures.
dc.relation.ispartofPhysical Review Materialsen
dc.rights© 2018, American Physical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at
dc.subjectDielectric propertiesen
dc.subjectQuantum criticalityen
dc.subjectRelaxor ferroelectricsen
dc.subjectQC Physicsen
dc.subjectTK Electrical engineering. Electronics Nuclear engineeringen
dc.titleQuantum critical points in ferroelectric relaxors : stuffed tungsten bronze K3Li2Ta5O15 and lead pyrochlore (Pb2Nb2O7)en
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.School of Chemistryen
dc.contributor.institutionUniversity of St Andrews.EaSTCHEMen
dc.contributor.institutionUniversity of St Andrews.School of Physics and Astronomyen
dc.contributor.institutionUniversity of St Andrews.Condensed Matter Physicsen
dc.description.statusPeer revieweden

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