Superior energy density through tailored dopant strategies in multilayer ceramic capacitors

The Gerson-Marshall (1959) relationship predicts an increase in dielectric breakdown strength (BDS) and therefore, recoverable energy density ( W rec ) with decreasing dielectric layer thickness. This relationship only operates however, if the total resistivity of the dielectric is sufficiently high...

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Published in:Energy & environmental science 2020-09, Vol.13 (9), p.2938-2948
Main Authors: Lu, Zhilun, Wang, Ge, Bao, Weichao, Li, Jinglei, Li, Linhao, Mostaed, Ali, Yang, Huijing, Ji, Hongfen, Li, Dejun, Feteira, Antonio, Xu, Fangfang, Sinclair, Derek C, Wang, Dawei, Liu, Shi-Yu, Reaney, Ian M
Format: Article
Language:English
Subjects:
Bismuth compounds
Capacitors
Conduction
Dielectric breakdown
Dielectric strength
Electrical resistivity
Energy
Ferroelectricity
Flux density
Homogeneity
Multilayers
Perovskites
Relaxors
Short circuits
Strontium titanates
Thickness
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Summary:The Gerson-Marshall (1959) relationship predicts an increase in dielectric breakdown strength (BDS) and therefore, recoverable energy density ( W rec ) with decreasing dielectric layer thickness. This relationship only operates however, if the total resistivity of the dielectric is sufficiently high and the electrical microstructure is homogeneous (no short circuit diffusion paths). BiFeO 3 -SrTiO 3 (BF-ST) is a promising base for developing high energy density capacitors but Bi-rich compositions which have the highest polarisability per unit volume are ferroelectric rather than relaxor and are electrically too conductive. Here, we present a systematic strategy to optimise BDS and maximum polarisation via : (i) Nb-doping to increase resistivity by eliminating hole conduction and promoting electrical homogeneity and (ii) alloying with a third perovskite end-member, BiMg 2/3 Nb 1/3 O 3 (BMN), to reduce long range polar coupling without decreasing the average ionic polarisability. These strategies result in an increase in BDS to give W rec = 8.2 J cm −3 at 460 kV cm −1 for BF-ST-0.03Nb-0.1BMN ceramics, which when incorporated in a multilayer capacitor with dielectric layers of 8 μm thickness gives BDS > 1000 kV cm −1 and W rec = 15.8 J cm −3 . Tailored dopant strategies are proposed to optimise the energy density of BiFeO 3 -SrTiO 3 , which can be adapted for other high polarisability oxide-based systems.
ISSN:1754-5692
1754-5706
DOI:10.1039/d0ee02104k