Go Su Hwan, Kim Kang San, Choi Ye Rok, Kim Jeong-Seog, Cheon Chae Il
Department of Materials Science & Engineering, Hoseo University, Asan 31499, Republic of Korea.
Department of Electronic Materials Engineering, Hoseo University, Asan 31499, Republic of Korea.
Materials (Basel). 2024 Sep 13;17(18):4492. doi: 10.3390/ma17184492.
The BiFeO-BaTiO (BF-BT) ceramics were here prepared through the solid-state reaction of BiO, FeO and nano-sized BT powders. The crystal structures and piezoelectric properties were investigated in both quenched (AQ) and slowly cooled (SC) 0.7BF-0.3BT ceramics. Prior work has shown that rhombohedral and pseudo-cubic phases coexist in 0.7BF-0.3BT ceramics. In this work, the crystal structure of the pseudo-cubic phase was refined as a non-polar orthorhombic Pbnm phase in the SC sample and as a polar orthorhombic Pmc2 phase in the AQ sample. In addition to a sharp dielectric peak at about 620 °C, corresponding to the Curie temperature of the rhombohedral phase, a broad dielectric peak with strong frequency dispersion and a sharp frequency-independent dielectric peak were observed at around 500 °C in the SC and AQ samples, respectively. We determine that the dielectric anomalies around 500 °C were caused by a relaxor phase transition of the non-polar orthorhombic phase in the SC sample and a ferroelectric-paraelectric phase transition of the polar orthorhombic phase in the AQ sample. The AQ sample showed better ferroelectric and piezoelectric properties than the SC sample. The 0.7BF-0.3BT ceramic slowly cooled in a nitrogen atmosphere showed a well-saturated P-E curve and a similar temperature-dependent dielectric constant as the AQ sample. Our results indicate that large concentrations of oxygen vacancies produce a more distorted polar orthorhombic phase and better piezoelectric properties in the AQ sample than in the SC sample.
本文通过BiO、FeO和纳米级BT粉末的固态反应制备了BiFeO-BaTiO（BF-BT）陶瓷。研究了急冷（AQ）和缓冷（SC）的0.7BF-0.3BT陶瓷的晶体结构和压电性能。先前的工作表明，0.7BF-0.3BT陶瓷中菱面体相和赝立方相共存。在本工作中，赝立方相的晶体结构在SC样品中被细化为非极性正交Pbnm相，在AQ样品中被细化为极性正交Pmc2相。除了在约620℃处对应菱面体相居里温度的尖锐介电峰外，在SC和AQ样品中分别在约500℃处观察到一个具有强频率色散的宽介电峰和一个与频率无关的尖锐介电峰。我们确定，500℃左右的介电异常是由SC样品中非极性正交相的弛豫相变和AQ样品中极性正交相的铁电-顺电相变引起的。AQ样品比SC样品表现出更好的铁电和压电性能。在氮气气氛中缓冷的0.7BF-0.3BT陶瓷显示出良好饱和的P-E曲线，并且与AQ样品具有相似的温度依赖性介电常数。我们的结果表明，与SC样品相比，大量的氧空位在AQ样品中产生了更扭曲的极性正交相和更好的压电性能。
