Mineralogy of the Silver King deposit, Omeo, Victoria

The Silver King mine (also known as Forsyths) operated very intermittently between about 1911 and the late 1940s on Livingstone Creek, near Omeo, in northeastern Victoria. The deposit consists of six thin and discontinuous quartz lodes that are variably mineralised. Assays of up to 410 ounces of silver per ton were obtained but there are only a few recorded production figures. Examination of representative ore samples shows that the main silver-bearing minerals in the primary ore are pyrargyrite, freibergite, andorite and the rare sulphosalt zoubekite, which occur irregularly with pyrite, arsenopyrite, galena and sphalerite. Phase assemblage data indicate that crystallisation occurred over an interval from about 450°C to less than 250°C, with the silver-bearing minerals crystallising at the lowest temperatures. The lodes were formed by the emplacement of hydrothermal solutions into fractures within the Ensay Shear Zone during the Early Devonian Bindian Orogeny. There are similarities in mineralisation and timing of emplacement between the Silver King lodes and the quartz-reef-hosted Glen Wills and Sunnyside goldfields 35‒40 km north of Omeo.

Microbe-Assisted Synthesis and Luminescence Properties of Monodispersed Tb3+-Doped ZnS Nanocrystals

Tb3+-doped zinc sulfide (ZnS:Tb3+) nanocrystals were synthesized by spray precipitation with sulfate-reducing bacterial (SRB) culture at room temperature. The morphology of the SRB and ZnS:Tb3+nanocrystals was examined by scanning electron microscopy, and the ZnS:Tb3+nanocrystals were characterized by X-ray diffractometry and photoluminescence (PL) spectroscopy. The PL mechanism of ZnS:Tb3+nanocrystals was further analyzed, and the effects of Tb3+ion concentration on the luminescence properties of ZnS:Tb3+nanocrystals were studied. ZnS:Tb3+nanocrystals showed a sphalerite phase, and the prepared ZnS:Tb3+nanocrystals had high luminescence intensity under excitation at 369 nm. The main peak position of the absorption spectra positively blueshifted with increasing concentrations of Tb3+dopant. Based on the strength of the peak of the excitation and emission spectra, we inferred that the optimum concentration of the Tb3+dopant is 5 mol%. Four main emission peaks were obtained under excitation at 369 nm:489 nm (5D4→7F6), 545 nm (5D4→7F5), 594 nm (5D4→7F4), and 625 nm (5D4→7F3). Our findings suggest that nanocrystals have potential applications in photoelectronic devices and biomarkers.

Crystal structure of quenched and in-field electroluminescent phosphors

Electroluminescent zinc sulfide doped with copper and chloride (ZnS:Cu, Cl) powder was heated to 400°C and rapidly quenched to room temperature. Comparison between the quenched and non-quenched phosphors using synchrotron radiation X-ray powder diffraction (XRPD) (λ = 0.828692 Å) and X-ray absorption spectroscopy (XAS) was made. XRPD shows that the expected highly faulted structure is observed with excellent resolution out to 150° 2θ (or to (12 2 2) of the sphalerite phase). The quenched sample compared to the unheated sample shows a large change in peak ratios between 46.7° and 46.9°, which is thought to correspond to the wurtzite (0 0 6), (0 3 2) and sphalerite (3 3 3)/(5 1 1) peaks. Hence, a large proportion of this sphalerite diffraction is lost from the material upon rapid quenching, but not when the material is allowed to cool slowly. The Zn K-edge XAS data indicate that the crystalline structures are indistinguishable using this technique, but do give an indication that the electronic structure has altered due to changing intensity of the white line. It is noted that the blue electroluminescence (EL) emission bands are lost upon quenching: however, a large amount of total EL emission intensity is also removed, which is consistent with our findings. We report the XRPD of a working alternating-current electroluminescence device in the synchrotron X-ray beam, which exhibits a new diffraction pattern when the device is powered in an AC field even though the phosphor is fixed in the binder. Significantly, only a few crystals are required to yield the diffraction data because of the high flux X-ray source. These in panel data show multiple sharp diffraction lines spread out under the region, where capillary data show broad diffraction intensity indicating that the phosphor powder is comprised of unique crystals, each having different structures.

Hydrothermal Synthesis and Luminescent Properties of Microtubes Constructed by Fluffy Zns:Mn2+ with Nanostructures

Tubular micrometer-sized ZnS:Mn2+ constructed by fluffy nanostructures were fabricated in the mixed solutions of water and ethanol in a fixed volume ratio with the aid of ethylenediamine. In the X-ray diffraction pattern, the products obtained in the presence and absence of ethylenediamine show the wurtzite and sphalerite phases, respectively. Field-emission scanning electron microscopic images reveal the evolution process from nanowires to fluffy ZnS:Mn2+ to microtubes with the reaction times of 2, 4, and 8 hours at 100 °C, and the basal nanowires are below 10 nm in diameter. Photoluminescence and photoluminescence excitation spectra were investigated. The results suggest that the wurtzite phase, instead of the sphalerite phase ZnS:Mn2+ is luminescence-active for the 4T1–6A1 transition of the Mn2+ in the ZnS host. The excitation spectra monitored at orange emission bands exhibit sharp peaks at 320, 326 and 327 nm with increasing reaction times of 2, 4, and 8 hours, respectively, indicating the energy transfer from ZnS host to Mn2+ ions, and the blue-shifts compared with the band gap absorption of the bulk counterpart (344 nm) are also observed due to the quantum confinement effects. The formation mechanism of the wurtzite one-dimensional nanostructures at such a low temperature is proposed based on a molecular template mechanism involving the bidentate coordinating ligand, ethylenediamine, and the possible formation mechanism of novel tubular structure are also discussed.