Crystal structure and thermal characteristics of Mn modified ultra-high curie temperature (>800 °C) Bi2WO6 piezoelectric ceramics

Searching low sintering temperature material with ultra-high Curie temperature (>800 °C) is urgent to seafloor hydrothermal vents detection. Bi2WO6 was first improved to possess ultra-high Curie temperature and ultra-high depolarization temperature by experiment. The MnCO3 was selected as dopant materials due to its excellent effect on improvement of sintering abilities and piezoelectric properties. The density test shows that Mn addition can obviously improve the density of Bi2WO6 ceramics from 93.6% to 97.76%, and the grains also changed from round to layered. The crystal structure change with Mn addition was tested by synchrotron radiation and calculated by ab initio and Rietveld refinement. The symmetry group of ultra-high Curie temperature Bi2WO6 is Aba2 (41). The XAFS results show that Mn atom more likely at the Bi-site in the crystal structure of Bi2W1-xMnxO6 and the Mn ion has the valence alternation. The Curie temperature of Bi2W1-xMnxO6 with increasing x are 997 °C, 915 °C, 890 °C, 729 °C, respectively, and the depolarization temperatures are around 940 °C, 895 °C, 825 °C, and 700 °C, respectively. The results show that Bi2W1-xMnxO6 (x ≤ 0.01) ceramics are suitable for the ultra-high temperature applications of sensors or transducers on seafloor hydrothermal vents detection.