Tin titanate – the hunt for a new ferroelectric perovskite
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We review all the published literature and show that there is no experimental evidence for homogeneous tin titanate SnTiO3 in bulk or thin-film form. Instead a combination of unrelated artefacts are easily misinterpreted. The X-ray Bragg data are contaminated by double scattering from the Si substrate, giving a strong line at the 2-theta angle exactly where perovskite SnTiO3 should appear. The strong dielectric divergence near 560K is irreversible and arises from oxygen site detrapping, accompanied by Warburg/Randles interfacial anomalies. The small (4μC/cm-2) apparent ferroelectric hysteresis remains in samples shown to be pure (Sn,Ti)O2 rutile/cassiterite, in which ferroelectricity is forbidden. Only very recent work reveals real bulk SnTiO3, but it possesses an ilmenite-like structure with an elaborate array of stacking faults, not suitable for ferroelectric devices. Unpublished TEM data reveal an inhomogeneous SnO layered structured thin films, related to shell-core structures. The harsh conclusion is that there is a combination of unrelated artefacts masquerading as ferroelectricity in powders and ALD films; and only a trace of a second phase in PLD film data suggests any perovskite content at all. The fact that X-ray, dielectric, and hysteresis data all lead to the wrong conclusion is instructive and reminds us of earlier work on copper calcium titanate (a well-known boundary-layer capacitor).
Gardner , J , Thakre , A , Kumar , A & Scott , J F 2019 , ' Tin titanate – the hunt for a new ferroelectric perovskite ' , Reports on Progress in Physics , vol. 82 , no. 9 , 092501 . https://doi.org/10.1088/1361-6633/ab37d4
Reports on Progress in Physics
Copyright © 2019 IOP Publishing Ltd. 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 may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1088/1361-6633/ab37d4
DescriptionThis work was supported in St Andrews by the Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/P024637/1.
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