Noncentrosymmetric Polar Oxide Material, Pb3SeO5: Synthesis, Characterization, Electronic Structure Calculations, and Structure-Property Relationships

A noncentrosymmetric (NCS) polar compound, Pb3SeO5, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Pb3SeO5 exhibits a two-dimensional crystal structure consisting of layers of alpha-PbO-like "slabs" that are linked through SeO3 polyhedia. Structurally, it is the bridging SeO3 Polyhedra between the alpha-PbO-like slabs that results in the NCS and polar nature of Pb3SeO5 Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicates that Pb3SeO5 exhibits a strong SHG efficiency of similar to 300 x alpha-SiO2 Additional SHG measurements indicate the material is type-I phase-matchable. Converse piezoelectric measurements revealed a d(33) value of similar to 81 pm/V, and a pyroelectric coefficient of -42 mu c/(m(2)K) at 65 degrees C was also determined Using first principle density functional theory (DFT) calculations, we demonstrated that polarization reversal in Pb3SeO5 is not energetically favorable-the material is polar but not ferroelectric. Our calculations also indicate that both Pb2+ and Se4+ cations exhibit a stereoactive lone-pair. In addition, differential scanning calorimetry measurements revealed in irreversible phase transition at similar to 440 degrees C. Finally, infrared, UV-vis and thermogravimetric measurements were also performed. Crystal data: Pb3SeO5, orthorhombic, space group Cmc2(1) (no. 36), a = 10 5211(13) angstrom, b = 10 7151(13) angstrom, c = 5.7452(7) angstrom, V = 647.68(14) angstrom(3), and Z = 2.