New Soft Chemical Routes to Ferroelectric SrBi₂Ta₂O₉

Abstract

Ferroelectric ceramics of strontium bismuth tantalate, SrBi 2 Ta 2 O 9 (SBT), have been synthesized in pure layer-structured perovskite phase by two new soft chemical techniques, namely, a sol-gel process and a coprecipitation method. The sol-gel process utilizes ethylene glycol as solvent while the coprecipitation technique makes use of a poly(ethylene glycol) 200 (PEG) and methanol mixture as solvent. The microstructure and properties of the ceramics have been studied and discussed. The sol-gel-derived ceramics sintered at 1200°C for 8 h show good dielectric and ferroelectric properties with a relative density of 96%, a dielectric constant ′ ) 227, a remnant polarization P r ) 7.6 µC/cm 2 at room temperature, and a maximum dielectric constant ′ max ) 950 at the Curie temperature T C ) 330°C. In comparison, the SBT ceramics prepared using the coprecipitation method and sintered under the same conditions show a platelike microstructure with preferential grain orientation along the [0010] direction, a relative density of 85%, an ′ of 235, a P r of 3.7 µC/cm 2 at room temperature, and an ′ max of 850 at T C ) 330°C. The sol-gel-derived ceramics show superior dielectric and ferroelectric properties than the ceramics prepared by the solid-state reactions ( ′ max ≈ 500 and P r ) 4.5 µC/cm 2 ), which can be attributed to a denser and more homogeneous microstructure with a better distribution of grain orientations, thus reducing the preferential grain orientation along the nonpolar c-axis.

Low-temperature synthesis of BiFeO3 nanopowders via a sol–gel method

“…Ethylene glycol has been proved to be a very good solvent to prepare metal oxides (i.e. SrBi 2 Ta 2 O 9 [17] and Ba 0.5 Sr 0.5 TiO 3 [14]) because the presence of two terminal hydroxyl groups in the molecule makes it easy for ethylene glycol to readily keep heterometallic units during hydrolysis reaction. It is reported that the linearly structured molecule of ethylene glycol is favorable for obtaining stable sol and acts as the template for a dense and linearly aligned structure of the precursor molecules [14].…”

Ferroelectric Bi4Ti3O12 and Bi4−x La x Ti3O12 ceramics prepared by a new sol-gel route

“…For comparison, the T C values for the same compounds were reported in [11] to be 425 and 400°C, respectively. The higher T C values found in our sol-gel processed ceramics are believed to result from a more stoichiometric composition of the samples which were treated and sintered at relatively low temperature, since it is well known that the loss of Bi-O species can lead to a lowering of T C [21]. From Fig.…”

“…In this paper, we report the synthesis of Bi 4 Ti 3 O 12 and Bi 4−x La x Ti 3 O 12 ceramics by an improved sol-gel method developed based on ethylene glycol following our recent work on the soft chemical synthesis of SBT ceramics [21]. Our main objective is to study the effect of sol-gel processing parameters and La-doping on the phase formation and dielectric properties of the BLT compounds.…”

An ethylene glycol-based new sol-gel route to multiferroic (1–x)LaCrO3–xBiCrO3 solid solution

“…It has been proved to be an effective solvent for the synthesis of complex oxides such as (1-x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 , [19][20][21][22] and Sr 2 Bi 2 Ta 2 O 9 . 23 Furthermore, the fine precursor powder obtained after the pyrolysis process, which possesses a large specific surface area and high reactivity, is advantageous in producing high-density ceramics, which is also necessary for achieving enhanced properties. …”