Negative capacitance in boracites: a structure-properties study at University of Dundee on FindAPhD.com

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Dr Charlotte Cochard No more applications being accepted Self-Funded PhD Students Only

Dundee United Kingdom Ceramics Experimental Physics Inorganic Chemistry Nanotechnology Solid State Physics

School of Science and Engineering, University of Dundee

About the Project

Boracites are a family of crystals of chemical formula M3B7O13X, with a structure composed of a framework of boron-oxygen tetrahedra, within which M and X ions are intercalated. Despite the first observation of the coupling between magnetism and ferroelectric properties (magnetoelectricity) being made in a boracite in the 60s [1], the oxyhalide system has gathered limited attention, largely due to the strong and versatile properties observed in perovskites. Recently, boracites have regained interest due to the existence of charged domain walls[2]. Domain walls are few unit-cells-thick interfaces separating domains of homogenous ferroic orders such as polarisation, magnetisation, or strain. They can be injected, annihilated, and repositioned by external bias such as electric field of stress making them interesting for novel computing applications such as memristors.

Some of the charged walls in Cu-Cl boracite are particularly perplexing as they move the “wrong way” under the application of an electric field; this generates a negative capacitance contribution to the dielectric response [3]. No such anomalous domain wall motion has ever been reported in any other ferroelectric system. Indeed, no physical mechanism has yet been proposed to explain such an energetically counterintuitive phenomenon and so further investigations are needed.

To improve the understanding of the origin of this negative capacitance, this project aims to grow new single crystals of boracite with different compositions, followed by the thorough characterisation of the structure and the dielectric and elastic properties of the material, especially at the phase transition. A better understanding of the role of the metal in the structure and on the phase transition will allow to propose a new model for negative capacitance in this system and will informed the future design of materials and devices.

For informal enquiries about the project, contact Dr Charlotte Cochard ([Email Address Removed])

For general enquiries about the University of Dundee, contact [Email Address Removed]

Our research community thrives on the diversity of students and staff which helps to make the University of Dundee a UK university of choice for postgraduate research. We welcome applications from all talented individuals and are committed to widening access to those who have the ability and potential to benefit from higher education.

QUALIFICATIONS

Applicants must have obtained, or expect to obtain, a UK honours degree at 2.1 or above (or equivalent for non-UK qualifications), and/or a Masters degree in a relevant discipline. For international qualifications, please see equivalent entry requirements here: www.dundee.ac.uk/study/international/country/.

English language requirement: IELTS (Academic) overall score must be at least 6.5 (with not less than 5.5 in reading, listening or speaking, and not less than 6.0 in writing). The University of Dundee accepts a variety of equivalent qualifications and alternative ways to demonstrate language proficiency; please see full details of the University’s English language requirements here: www.dundee.ac.uk/guides/english-language-requirements.

APPLICATION PROCESS

Step 1: Email Dr Charlotte Cochard ([Email Address Removed]) to (1) send a copy of your CV and (2) discuss your potential application and any practicalities (e.g. suitable start date).

Step 2: After discussion with Dr Cochard, formal applications can be made via our direct application system. When applying, please follow the instructions below:

Candidates must apply for the Doctor of Philosophy (PhD) degree in Physics (3 Year) using our direct application system: apply for Physics.

Please select the study mode (full-time/part-time) and start date agreed with the lead supervisor.

In the Research Proposal section, please:

- Enter the lead supervisor’s name in the ‘proposed supervisor’ box

- Enter the project title listed at the top of this page in the ‘proposed project title’ box

In the ‘personal statement’ section, please outline your suitability for the project selected.

Funding Notes

There is no funding attached to this project. The successful applicant will be expected to provide the funding for tuition fees and living expenses, via external sponsorship or self-funding.

References

[1] H. Schmid, “The dice - Stone der würfelstein: Some personal souvenirs around the discovery of the first ferromagnetic ferroelectric,” Ferroelectrics, vol. 427, no. 1, pp. 1–33, 2012.
[2] R. G. P. McQuaid, M. P. Campbell, R. W. Whatmore, A. Kumar, and J. M. Gregg, “Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite,” Nat. Commun., vol. 8, no. May, p. 15105, 2017.
[3] J. G. M. Guy, C. Cochard et al., “Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite,” Adv. Mater., vol. 33, p. 2008068, 2021.

Where will I study?

University of Dundee

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