title: Structure and physical properties of the polar oxysulfide CaZnOS.
abstract: The synthesis, structure, and electrical properties of the oxysulfide CaZnOS are reported. The white compound has a band gap of 3.7(1) eV and crystallizes in hexagonal space group P6(3)mc (No. 186) with a = 3.75726(3) A, c = 11.4013(1) A, and Z = 2. The noncentrosymmetric structure, which has few analogues, is composed of isotypic puckered hexagonal ZnS and CaO layers arranged so that ZnS3O tetrahedra are all aligned parallel, resulting in a polar structure. The compound shows type 1 non-phase-matchable second harmonic generation, determined using 1064 nm radiation, with an efficiency approximately 100 times that of alpha-SiO2 and a piezoelectric coefficient of 38 pm V-1. Although polar, CaZnOS is not ferroelectric and the pyroelectric coefficient is very small, approximately 0.0 microC m-2 K-1 between room temperature and 100 degrees C.
authors.affiliation: Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
authors.forename: Timothy
authors.initials: T
authors.lastname: Sambrook
authors.forename: Catherine F
authors.initials: CF
authors.lastname: Smura
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Clarke
authors.forename: Kang Min
authors.initials: KM
authors.lastname: Ok
authors.forename: P Shiv
authors.initials: PS
authors.lastname: Halasyamani