Growth and Characterisation of Layered (BA)2CsAgBiBr7 Double Perovskite Single Crystals for Application in Radiation Sensing

A recent publication on single crystals of two-dimensional, layered organic–inorganic (BA)2CsAgBiBr7 double perovskite (BA+ = CH3CH23NH3+) suggested the great potential of this semiconductor material in the detection of X-ray radiation. Our powder XRD measurement confirms the crystallinity and purity of all samples that crystallise in the monoclinic space group P21/m, while the single crystal XRD measurements reveal the dominant {001} lattice planes. The structure–property relationship is reflected in the lower resistivity values determined from the van der Pauw measurements (1.65–9.16 × 1010 Ωcm) compared to those determined from the IV measurements (4.19 × 1011–2.67 × 1012 Ωcm). The density of trap states and charge-carrier mobilities, which are determined from the IV measurements, are 1.12–1.76 × 1011 cm–3 and 10−5–10−4 cm2V–1s–1, respectively. The X-ray photoresponse measurements indicate that the (BA)2CsAgBiBr7 samples synthesised in this study satisfy the requirements for radiation sensors. Further advances in crystal growth are required to reduce the density of defects and improve the performance of single crystals

New economy initial public offerings in Australia

This study provides insights to the short and long-term performance of the Initial Public Offerings (IPOs) for new economy companies that listed on the Australian Stock Exchange in the period 1995 to 2000. New economy IPOs provided high average initial returns to subscribing investors although there is also evidence on severe overpricing. However, despite these high initial returns, Australian new economy IPOs do not on average under perform the market benchmark in the long run. The presence of some highly overpriced initial equity offerings provides support for the existence of informational asymmetry between informed (institutional) and uninformed (retail) investors in the Australian new economy IPO market

Can Information Made Publicly Available Explain Long-Term Performance of New Economy Seasoned Equity Offers?

Seasoned equity offers, Long-term returns, New economy

Use of in situ Hf-isotope analyses of zircon to interpret granitoid magma genesis

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Lithospheric mantle evolution beneath northeast Australia

New in situ analyses of Re-Os systematics in single grains of sulfides in Cainozoic basalt-borne spinel lherzolite xenoliths from the Chudleigh Province (Australian craton) and Atherton Province (Tasman Fold Belt) are reported. The sulfide data and previously reported U-Pb and Hf-isotope data for detrital zircons and zircons from granitoids (Murgulov et al., 2007; 2009) show correlations between mantle events and crustal magmatism in northeast Queensland, Australia. About half of the analysed sulfide grains have sub-chondritic 187Os/188Os (0.1130-0.1252) and 187Re/188Os (0.0214-0.2061), suggesting preservation of their isotopic signatures during subsequent infiltration of asthenospheric silicate melts/fluids. Collision and accretion processes have probably initiated a melt-extraction event followed by cratonic lithosphere stabilisation at ~2.2Ga (TMA model age). Metasomatism of the mantle lithosphere most likely involved infiltration of asthenospheric melts/fluids during lithospheric thinning and rifting beneath the Chudleigh Province at ~1.82Ga, 0.81Ga and 0.35Ga (TRD Rhenium-depletion model ages), beneath the Atherton Province at ~1.75Ga and 0.44Ga (TRD), and during suturing at ~1.23Ga (TRD), an event recorded beneath both provinces. In the Georgetown Inlier TRD model ages coincide with episodes of granitoid production and demonstrate a close temporal linkage between events in the cratonic lithospheric mantle and crust. However, such linkages cannot be demonstrated in the Tasman Fold Belt; no ~0.44Ga, 1.23Ga or 1.75Ga granites outcrop in this region, and the shallow part of the subjacent lithospheric mantle (~27km depth) experienced a younger (~0.44Ga) metasomatic event not observed in the deeper lithosphere (~49km depth, ~1.75Ga). The younger event may be associated with the reactivation of ancient lithospheric sutures during mantle upwelling and back-arc rifting. The older events may imply that the edge of the cratonic lithospheric mantle root, metasomatised at ~1.75Ga and 1.23Ga, was rifted during a younger event (~0.44Ga?). Its scattered fragments have been embedded at greater depth within the lithospheric mantle beneath the Atherton Province following collision, accretion and lithosphere suturing.18 page(s

Carboniferous and Permian granites of the northern Tasman orogenic belt, Queensland, Australia : insights into petrogenesis and crustal evolution from an in situ zircon study

In situ U-Pb dating and Lu-Hf systematics of zircon in granites of the Hodgkinson Province in the northern Tasman orogenic belt, Queensland, Australia, reveal input of isotopically more evolved crustal magmas and larger ranges in ¹⁷⁶Hf/¹⁷⁷Hf in the Carboniferous I-type granites (0. 28219-0. 28269; weighted average ~0. 28245) than in the Permian S-type granites (0. 28249-0. 28280; weighted average ~0. 28262) and Permian I-type granites (0. 28253-0. 28274; weighted average ~0. 28260). The wide range in the Hf-isotope compositions of zircons in the Carboniferous and Permian granites can be explained by remelting of a heterogeneous Mesoproterozoic crustal source, whereas a narrow range reflects the subsequent dissolution of inherited grains/cores and magma homogenisation before zircon crystallisation. Alternatively, mixing between the most radiogenic and unradiogenic magmas can produce the isotopic variation seen in other Carboniferous granites. Remelting of Neoproterozoic average crust or mafic younger crust can produce the more radiogenic Hf-isotope compositions of zircons in the Permian S-type granites. An overlap between the Hf-isotope signatures of the Carboniferous I-type granites in the southwestern Hodgkinson Province and the northeastern Australian craton (0. 28211-0. 28254) and evidence for major magmatic events at 1,585-1,545 and 345-300 Ma imply that the southwestern province is underlain by cratonic crust, which wedges out towards the northeast. The more radiogenic Hf-isotope signature of the Permian granites and a lack of evidence for these major magmatic events in the southeastern and central Hodgkinson Province imply that these parts are characterised by different crustal sources and crustal evolution histories.23 page(s

Temporal correlation of magmatic-tectonic events in the lower and upper crust in north-east Australia

Hf model ages yielded by rutiles in a garnet-rich lower-crustal granulite xenolith from the McBride Province and whole-rock Nd and Hf model ages for the plagioclase- and garnet-rich Chudleigh and McBride granulites overlap with the well-defined U-Pb ages for detrital zircons and zircons in granitoids (Murgulov et al. Chem Geol 245:198-218, 2007; Mineral Petrol 95:17-45, 2009), suggesting temporal correlation of magmatic-tectonic events in the lower and upper crust in the north-east Australian craton. Intrusion of basaltic magmas into and below the lower crust beneath the Chudleigh Province around 1.4, 1.7 and 2.3 Ga and beneath the McBride Province around 1.5, 1.7, 2.3 and 2.5 Ga provided heat for remelting and supplied magmas with juvenile mantle isotope signatures to the upper crust. Similar magmas provided enough heat to cause melting in the lower crust beneath the Chudleigh Province around 0.12 and 0.8-0.9 Ga and beneath the McBride Province around 0.42, 0.8-0.9 Ga, 1.1 and 1.3 Ga but were not sufficient to cause significant melting in the upper crust. A wide range in initial ¹⁷⁶Hf/¹⁷⁷Hf values and a ~1.55 Ga Hf model age yielded by rutiles in the McBride granulite provide a link to the genesis of ~420 Ma granitoids. The data for a plagioclase-rich granulite from the Atherton Province are similar to those for the Chudleigh and McBride granulites. However, additional samples are required to test whether the lower crust of the Tasman orogenic belt is lithologically and isotopically similar to the lower crust of the craton.19 page(s

Temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the Lochaber Ring Dyke Complex, North Queensland, Australia : insights from in situ U–Pb and Hf-isotope analysis of zircon

An existing model for the temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the nearby Lochaber Ring Dyke Complex has been evaluated using in situ U–Pb and Hf-isotope analyses of zircon grains. The Oak River Granodiorite, the host rock to the Kidston Breccia Pipe, has 1,551 ± 6 Ma old zircon cores overgrown by 417.7 ± 2.2 Ma rims. The Black Cap Diorite and Lochaber Granite within the Lochaber Ring Dyke Complex have crystallisation ages of 350.7 ± 1.3 and 337.9 ± 2.6 Ma respectively. The gold-rich Median Dyke within the Kidston Breccia Pipe has a crystallisation age of 335.7 ± 4.2 Ma, and thus is temporally related to the Lochaber Granite. However, zircon grains from the Median Dyke have less radiogenic Hf-isotope compositions (ɛ Hf from −7.8 to −15.8) than those from the Black Cap Diorite ɛHf = 0.4 to −7.2) and the Lochaber Granite (ɛ Hf = −1.0 to −7.5), but within the range defined by zircons from the Oak River Granodiorite ɛ Hf  = −8.0 to −29.2). The Hf-isotope data thus rule out the proposed fractional crystallisation relationship between the Kidston gold-bearing rocks and the Lochaber Ring Dyke Complex. The Kidston Median Dyke may have been produced by mixing between Lochaber Granite magmas and magmas derived by remelting of the Oak River Granodiorite, which was itself derived from Proterozoic crust. There is no evidence for a juvenile component in the Lochaber Ring Dyke Complex or the Median Dyke. The gold enrichment in the Kidston rocks thus may reflect the multi-stage reworking of the Proterozoic crust, which ultimately produced the Carboniferous felsic magmas.29 page(s