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Large picosecond nonlinearities in Ba 0.5 Sr 0.5 TiO 3 thin films, grown at different temperatures in situ on ͑100͒ MgO substrates using rf magnetron sputtering technique, were studied using the Z-scan technique. The nonlinear absorption mechanism, studied near 800 nm using ϳ2 and 25 ps pulses, switched from reverse saturable absorption type in the films deposited at temperatureϽ 600°C to three-photon absorption ͑3PA͒ in the films deposited at temperatureϾ 600°C. The magnitude of the 3PA coefficient was estimated to be ϳ10 −21 cm 3 / W 2. Two-photon absorption ͑2PA͒ was the dominant mechanism recorded with ϳ6 ns pulses. The observed behavior is correlated with morphological and crystallographic texture of the films. The linear refractive index and optical band gap of the films have also been calculated and these show a strong dependence on the substrate temperature.

Mystristic capped CdSe QDs with schematic diagram and formation mechanism of bio-taggable CdSe@ZnS QDs.

Driven by the need for high-temperature ntype thermoelectrics for energy-harvesting sectors, SrTi 0.8 Nb 0.2 O 3±δ ceramics are prepared here from powders with average particle sizes of 270 and 800 nm by the conventional sintering in air at 1450 °C and further in H 2 /N 2 at 1400 °C. In contrast to coarse particle powders, the use of fine particle powders under these conditions leads to abnormal grain growth and thereby bimodal grain size distribution in SrTi 0.8 Nb 0.2 O 3±δ ceramics. As a result, a 3fold increase in the thermoelectric figure of merit to 0.36 at 970 K is achieved, thus establishing the record value for bulk Nb-doped strontium titanate up to this temperature.

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