Group 16 solid state compounds: Synthetic methods and applications

The work presented here encompasses three topics all dealing with the synthesis of new group 16 compounds: sulfide compounds for nonlinear optical (NLO) materials; telluride compounds for potential thermoelectric applications; and oxide-based luminescent materials.; Nonlinear optical materials are important for a wide range of laser applications, as well as for the development of completely optical fiber based technology. Many oxide based NLO systems are known to work well in the UV and visible regions of the spectrum, but all of these materials become absorbing by around 4-5 {dollar}mu{dollar}m. Sulfides, however, have a wider transmission range into the infrared making them potentially useful in the atmospheric window around 10 {dollar}mu{dollar}m. Since ferroelectric materials can be used for quasi-phase matching, the goal of the work presented here was to find new ferroelectric sulfides.; The {dollar}rm Lasb6Msb{lcub}x{rcub}Mspprimesb2Ssb{lcub}14{rcub}{dollar} family (M = a variety of monovalent, divalent, and trivalent elements, M{dollar}spprime{dollar} = Si or Ge), is an extensive group of noncentrosymmetric compounds which have been predicted to undergo ferroelectric transitions at temperatures up to 1000 K. Therefore, this family was of interest in our search for ferroelectric sulfides.; A new compound in this family, {dollar}rm Lasb6MgGesb2Ssb{lcub}14{rcub},{dollar} has been synthesized and the structure determined. Another curious phase with a composition of {dollar}rm Lasb6Sisb{lcub}x{rcub}Ssb{lcub}14{rcub} (x>2){dollar} was also discovered. Possible twinning problems related to the domain structure have complicated the structural refinements of this material. The structure of {dollar}rm Lasb6MgGesb2Ssb{lcub}14{rcub}{dollar} is reported as well as the details of the work on the {dollar}rm Lasb6Sisb{lcub}x{rcub}Ssb{lcub}14{rcub}{dollar} compound.; A secondary project focused on the search for small band gap tellurides for possible thermoelectric applications. A study of four systems, Bi/Ni/Te, Ce/X/Te, La/X/Te, and Ba/X/Te (where X is Bi, Pb, Ge, Ga, Sn, In, and Sb) was undertaken in hopes of finding new ternary phases related to Bi{dollar}sb2{dollar}Te{dollar}sb3,{dollar} the best currently known thermoelectric material. Unfortunately, mostly known binary and ternary phases resulted.; The final project discussed deals with combinatorial chemistry, a relatively new technique just now being applied to materials issues. This work was done in conjunction with Symyx Technologies and focused on the synthesis of borate luminescent materials via combinatorial techniques.