Colossal dielectric permittivity of BaTiO3-based nanocrystalline ceramics sintered by spark plasma sintering

Abstract

In pursuit of high permittivity materials for electronic application, there has been a considerable interest recently in the dielectric properties of various perovskite oxides like calcium copper titanate or lanthanum doped barium titanate. When processed in a particular way, this later material present at ambient temperature and at f= 1 kHz unusual interesting dielectric properties, a so called "colossal" permittivity value up to several 10 6 with relatively low dielectric losses. Moreover and contrary to what is classically expected and evidenced for this type of materials, no temperature dependence is observed. This behavior is observed in nanopowders based ceramics. An assumption to explain the observed properties is proposed. These results have important technological applications, since these nanoceramics open a new route to the fabrication of very thin dielectric films.

Phase stabilization in plasma sprayed BaTiO3

“…Detailed microstructural investigation of this sample was however not performed. The detected ''colossal permittivity'' [3] values (over 200,000), elsewhere called ''supercapacitor features'' [10], are in agreement with our results.…”

“…In general, there are differences in the behavior of barium titanate in the form of a single crystal, sintered bulk material, thin film and spark plasma sintered disks [2][3][4]. Plasma spraying enables creation of layers with ''bulk-like'' thickness but adhering to a metallic substrate of various shapes.…”

Application of spark plasma sintering to processing of dense Ba(Ti1−xSnx)O3 (x=0.13) ceramic

“…In the volume, samples were dark blue due to the reducing sintering atmosphere used during SPS (low vacuum). In this way, some Ti 4+ is reduced to Ti 3+ , a well-known phenomena in SPS sintering [19]. To restore the oxygen stoichiometry and to remove the carbon contamination, SPS dense pellets were annealed in oxygen, at 1100 • C for 5 h.…”

“…it involves occurrence of hot spots and much debated plasma states, leading to non homogeneities and defects. Up to now, SPS was used with good results for sintering of BaTiO 3 [19][20][21] ceramics starting from powders produced by solid-state reaction between oxides and carbonates. In this paper, we used SPS to obtain single phase solid solution Ba(Ti 1−x Sn x )O 3 (x = 0.13) as a high density ceramic.…”

Blocking effect of crystal–glass interface in lanthanum doped barium strontium titanate glass–ceramics

“…Although the defect chemistry of undoped and doped barium titanate (BaTiO 3 ) ceramics is well studied [9][10][11], many discrepancies still exist between experimental results and theoretical interpretations, especially for lanthanum doped barium titanate glass-ceramics [12,13]. Colossal dielectric permittivity was observed in Ba 0.95 La 0.05 TiO 3Àx ceramics [14,15]. This effective permittivity is attributed to interfacial polarization, which is formed between semiconducting grains and insulating grain boundaries in the ceramics.…”