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Not AvailableA series of calcium rare earth silicate chlorides, CaLnSiO4Cl (Ln = Pr, Nd, Sm, Eu, Gd, and Tb), was obtained as single crystals from flux crystal growth. The structures were determined by single crystal X-ray diffraction and were found to be related to the spodiosite /Wagnerite mineral structure, Ca2PO4F. The obtained compositions are variations of the spodiosite structure that result from two simultaneous elemental substitutions. Replacing one calcium for one rare earth element and the simultaneous replacement of one VO43- or PO43- with one SiO44-. CaEuSiO4Cl was found to luminesce, and its photoluminescence spectrum is reported. 

A flux growth method for the high-yield synthesis of Pb10(PO4)6O single crystals was developed. This optimized synthesis method was utilized for the systematic doping of copper into the lead apatite structure, where the availability of single crystals allowed for a detailed structural analysis via single crystal X-ray diffraction. Our developed synthesis method resulted in a different type of copper doping in lead apatite where instead of Cu(II) doping onto the lead sites, doping occurred via Cu(I) doping into the disordered channels at the center of the Pb(1)/Pb(2) columns in the form of CuO2 linear units. The presence of Cu(I) as opposed to Cu(II) in the structure was shown via magnetic susceptibility data which also indicated a lack of superconductivity in the modified lead apatite at all achieved doping levels. The knowledge gained from this study enabled a reanalysis of the initial diffraction data reported for LK-99. While this work further supports the lack of superconductivity in the modified lead apatites, it does allow us to suggest a more accurate formula for LK-99: Pb10(PO4)6(CuO)2O1-1.5x. 

Mild hydrothermal synthesis was employed to grow high-quality single crystals of ternary fluoridohafnates at low temperatures. The series of new materials was characterized using single crystal X-ray diffraction, and the crystal structures for AHfF6 (A= Mg and Sr), A2HfF8 (A= Ba and Pb), Ca5Hf3F22 and Cd2HfF8(H2O)6 are discussed herein. Although some material compositions have similar stoichiometries, all the compositions adopt different structural motifs. A comparison of the crystal structures and synthesis techniques of ternary fluoridohafnates and ternary fluoridozirconates is also reported, and the impact of the subtle changes of synthesis conditions on overall structures is discussed.