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Observation of a Polar Compound with Halide Ordering in the Compositional Series (CH3NH3)2Te(BrxCl1-x)6
Yuhan Liu1,2, Prajna Bhatt1,3, Roxy Lee1,4
1Department of Chemistry, University College London, 20 Gordon St, London WC1H 0AJ, U.K.
Abstract:
Single-crystal samples of compounds in the series (CH3NH3)2Te(Cl1-xBrx)6 were produced with counter-diffusion crystal growth in silica gels, and new crystal structures are determined using single-crystal X-ray diffraction. With increasing Br content, the structure transitions from P3̅m1 to P63mc to R3̅m and finally to Fm3̅m. The compound with x≈0.068 adopts the polar P63mc space group, and the structure has partially ordered Cl- and Br- ions. The crystals of this compound show distinct piezoelectric domains with different responses by Piezoresponse Force Microscopy (PFM), confirming their polar structure.
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