Structure-composition-property relationships in complex ACu3B4O12 perovskites

Lead Research Organisation: University of Sheffield
Department Name: Materials Science and Engineering


Preliminary results in our laboratory have shown two members (CaCu3Ti4O12, CCTO, and Na1/2Bi1/2Cu3Ti4O12) from a large family of perovskite-related compounds based on the general formula ACu3B4O12 have high intrinsic permittivity (> 100) at low temperatures and that appropriate doping (with Mn) can produce ceramics with encouraging microwave dielectric resonance properties at room temperature. The large values of intrinsic permittivity suggests some (as yet unknown) form of additional polarisation, other than ionic polarisation plays an important role in these compounds and that ACu3Ti4O12-type materials possess fundamentally interesting dielectric behaviour and potentially useful bulk dielectric properties after appropriate chemical doping. The aim of this study is therefore to prepare and characterise a wide variety of undoped and Mn-doped ACu3B4O12-type compounds to establish their structure-composition-property relationships. Particular emphasis will be given to optimising the bulk dielectric properties to assess their potential as commercially-useful high permittivity and/or temperature-stable dielectrics.


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Ferrarelli M (2009) Possible incipient ferroelectricity in Mn-doped Na1/2Bi1/2Cu3Ti4O12 in Applied Physics Letters

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Ferrarelli M (2011) Microwave dielectric properties of Na 1/2 Bi 1/2 Cu 2.82 Mn 0.18 Ti 4 O 12 ceramics in IOP Conference Series: Materials Science and Engineering

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Fiorenza P (2010) Detection of heterogeneities in single-crystal CaCu 3 Ti 4 O 12 using conductive atomic force microscopy in IOP Conference Series: Materials Science and Engineering

Description Discovered that CaCu3Ti4O12 (CCTO) is a barrier layer capacitor material and that the giant permittivity effect is associated with a Maxwell Wagner effect. This occurs when the grains are semiconducting and the grain boundaries are insulating.

Related materials, eg (Na,Bi)Cu3Ti4O12 also show similar effects. We developed doping mechanisms to suppress the leakage conductivity (i.e. Mn for Cu) and to reveal the intrinsic dielectric properties. These materials are incipent ferroelectrics with high permittivity, in the range of 80 -120, however they have quite strong temperature dependence and this means they cant be used as microwave dielectric materials for resonators or filters.
Exploitation Route Other groups are investigating this CCTO class of perovskites. for other potential functional applications, such as thermoelectrics.
Sectors Digital/Communication/Information Technologies (including Software),Electronics

Description New and Improved Electroceramics
Amount £3,658,771 (GBP)
Funding ID EP/G005001/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2008 
End 03/2013