Molten Alkali Halide Flux Growth of an Extensive Family of Noncentrosymmetric Rare Earth Sulfides: Structure and Magnetic and Optical (SHG) Properties

Mohammad Usman; Mark D Smith; Gregory Morrison; Vladislav V Klepov; Weiguo Zhang; P Shiv Halasyamani; Hans-Conrad Zur Loye

doi:10.1021/acs.inorgchem.9b00849

Molten Alkali Halide Flux Growth of an Extensive Family of Noncentrosymmetric Rare Earth Sulfides: Structure and Magnetic and Optical (SHG) Properties

Inorg Chem. 2019 Jul 1;58(13):8541-8550. doi: 10.1021/acs.inorgchem.9b00849. Epub 2019 Jun 19.

Authors

Mohammad Usman¹, Mark D Smith¹, Gregory Morrison¹, Vladislav V Klepov¹, Weiguo Zhang², P Shiv Halasyamani², Hans-Conrad Zur Loye¹

Affiliations

¹ Department of Chemistry and Biochemistry , University of South Carolina , Columbia , South Carolina 29208 , United States.
² Department of Chemistry , University of Houston , Houston , Texas 77204 , United States.

PMID: 31247854
DOI: 10.1021/acs.inorgchem.9b00849

Abstract

Twenty new alkali rare earth thiosilicates and thiogermanates with the general formula ALnTS₄ (A = alkali metal, Ln = lanthanide, and T = Si, Ge) were grown as X-ray diffraction-quality single crystals from molten alkali chloride fluxes. These include KNdSiS₄, KPrSiS₄, RbLnSiS₄ (Ln = Ce, Pr, Nd, Gd, Tb, Dy, and Ho), RbLaGeS₄, CsLnSiS₄ (Ln = La, Pr, and Nd), and CsLnGeS₄ (La, Ce, Pr, Nd, Eu, Gd, and Tb). Herein, we discuss the use of a molten chloride flux growth approach for the preparation of the title compounds and their structure determination via single-crystal X-ray diffraction. In addition, we comment on the magnetic properties of RbNdSiS₄, CsNdSiS₄, CsNdGeS₄, and CsGdGeS₄, which were found to be paramagnetic for T = 2-300 K and exhibited negative Weiss temperatures with no obvious antiferromagnetic transition down to 2 K. The optical properties of CsLaGeS₄ and CsNdTS₄(T = Si, Ge) were measured by UV-vis spectroscopy. Second harmonic generation measurements performed on CsLaGeS₄ confirmed the crystallization of the compound in the noncentrosymmetric orthorhombic space group, P2₁2₁2₁; CsLaGeS₄ was found to be SHG-active with nearly half the intensity of α-SiO₂ upon irradiation with a Nd:YAG 1064 nm laser, and a semiconductor exhibiting a band gap of 3.60 eV based on UV-vis diffuse reflectance measurements.