Li0.5Bi2.5Nb2O9: An alkali-metal bismuth layer structured ferroelectric with high T-C and small orthorhombic distortion

Bismuth layer structured ferroelectrics (BLSFs) have drawn much attention due to their great potential for high-temperature applications. It is generally accepted that BLSFs with small orthorhombic distortion should have low T-C. In this paper, we report an anomalous example Li0.5Bi2.5Nb2O9 (LBN), which has small orthorhombic distortion but very high T-C. LBN shows the highest T-C (834 degrees C) among currently reported prototype alkali-metal BLSFs, which is attributed to its small tolerance factor. However, the refinement result reveals that LBN is orthorhombic with the space group of A2(1)am, and the orthorhombic distortion of LBN a/b is merely 1.0019. The measurement of piezoelectric coefficient (d(33) similar to 6 pC/N) and observation of striped domain structure confirm the ferroelectricity nature of LBN. This work deepens our understanding of BLSFs and may lead to the finding of more novel BLSFs with high performance.