Microstructure and electrical properties of Aurivillius phase (CaBi2Nb2O9)1−x(BaBi2Nb2O9)x solid solution

Abstract

Articles you may be interested inThe microstructures and electrical properties of Aurivillius phase ferroelectric solid solutions of ͑CaBi 2 Nb 2 O 9 ͒ 1−x ͑BaBi 2 Nb 2 O 9 ͒ x ͑0 Յ x Յ 1͒ have been studied. X-ray diffraction analyses revealed a bismuth layered structure for all compositions. Scanning electron microscope images showed randomly oriented and platelike grain morphology. The Curie point T c or the maximum permittivity temperature T m decreased with increasing x. The ͑CaBi 2 Nb 2 O 9 ͒ 1−x ͑BaBi 2 Nb 2 O 9 ͒ x ceramics exhibited a ferroelectric-paraelectric phase transition at small x values ͑x Յ 0.5͒, whereas a relaxor behavior was observed at high x values ͑x Ն 0.8͒. The d 33 value of CaBi 2 Nb 2 O 9 ceramics was enhanced by Ba 2+ doping on the A-sites ͑x Յ 0.3͒. A combination of high d 33 values and high T c points ͑Ͼ700°C͒ suggests that compositions with x Յ 0.3 could be good candidates for high-temperature piezoelectric applications. The composition with x = 0.8 is a relaxor ferroelectric with T m around 320°C at 1 MHz.

Grain oriented growth and properties of ultra-high temperature CaBi2Nb2O9 piezoelectric ceramics

“…Therefore, according to the oriented alignment degrees of ceramic grains, f is between 0 and 1. The larger f is, the higher the orientation degree becomes [10][11][12][13][14][15][16][17]. By calculations, the ceramics prepared by new technique reach a 43% orientation degree, which indicates that ceramic grains brow along a specific direction to realize textured ceramics.…”

“…Since the transfer rate in molten salt is far higher than that in solid phase, the molten salt method can significantly reduce the reaction temperature and time. Meanwhile, the grain size and shape can be effectively controlled using molten salt method so as to synthesize powders with specific morphology [5,[13][14][15][16]. Grain alignment in such powders exhibits elementary selective orientation in the dry-press process due to pressure gradient.…”

“…For the ceramics prepared by the new technique, the compactness is enhanced with oriented grain growth, resulting in much easier domain reversion. Therefore, polarization at room temperature becomes much easier [5][6][7][8][11][12][13][14][15]. By putting the samples into silicon oil, the piezoelectric performances were measured after a 30-min polarization under 120 kV/cm direct current to get the piezoelectric constant d 33 = 10~12 pC/N.…”

“…Technique improvement usually adopt grain-orientation techniques to realize textured ceramics and thus to produce single-crystal-like anisotropy. Some commonly used techniques are sparkling plasma sintering, hot-forging, hot-pressing, templated grain growth and reactive templated grain growth [11][12][13][14][15]. However, the above techniques are costly and complicated, unsuitable for industrial producing.…”

“…However, their performances are limited by the spatially two-dimensional structure due to spontaneous polarization orientation, which brings them disadvantages such as high coercive field E c , difficult polarization and low piezoelectric activity [7][8][9][10]. Recently, many researches have been carried out on developing bismuth layer-structured piezoelectric ceramics by researchers all over the world [5][6][7][8][9][10][11][12][13][14][15]. Of those works, the most representative ones including Yan from Queen Mary University of London, Zhang from Pennsylvania State University, Tsuzuki from Waseda University and Damjanovic from EPFL Lab of Switzerland.…”