Average Crystallite Grain Size Research Articles

Synthesis, electrical and ultrafast nonlinear optical properties of Sn–ZnO composite film

Tin (Sn)- zinc oxide (TZO) composite films were successfully synthesized by the magnetron sputtering. Structure and morphology of the TZO composite films with different sputtering conditions (growth time, direct current sputtering powers and substrate temperature) were characterized. X-ray diffraction (XRD) patterns confirmed characteristic peaks of ZnO and SnO2 without any alloys distinct phases. The scanning electron microscope (SEM) micrographs revealed that the average grain size of crystallites was found to increase with increasing growth time and sputtering powers, respectively. The optical, electrical and ultrafast nonlinear optical characterizations of the TZO composite films with different growth time were studied. The effect of Sn content on the optical and electrical properties of the TZO composite films was analyzed. As growth time increasing, the optical gap of TZO composite films increased and then decreased. The Hall test results showed that Sn enhanced the carrier concentration of ZnO film. The carriers of TZO composite films range from 10−15 to 10−19/cm3 in concentration. Meanwhile, from the femtosecond Z-scan experimental results, the samples showed the change from reverse saturable absorption to saturable absorption with increasing growth time. The values of the nonlinear absorption coefficient for the TZO composite films with four growth time were 4.628 × 10−7 m/W, 6.016 × 10−8 m/W, 5.245 × 10−8 m/W and 4.407 × 10−8 m/W, respectively. The ease of the synthesis route and the remarkable electrical and ultrafast nonlinear optical properties offer TZO films as a promising electron source for high current density and nonlinear optical applications.

Influence of Sn content on properties of ZnO:SnO2 thin films deposited by ultrasonic spray pyrolysis

The present work is devoted to the preparation of zinc oxide (ZnO): tin oxide (SnO2) thin films by ultrasonic spray technique. A set of films are deposited using a solution formed with zinc acetate and tin chloride salts mixture with varied weight ratio R=[Sn/(Zn+Sn)]. The ratio R is varied from 0 to 100% in order to investigate the influence of Sn concentration on the physical properties of ZnO:SnO2 films. The X rays diffraction (XRD) analysis indicated that films are composed of ZnO and SnO2 distinct phases without any alloys or spinnel phase formations. The average grain size of crystallites varies with the ratio R from 17 to 20nm for SnO2 and from 24 to 40nm for ZnO. The obtained films are highly transparent with a transmission coefficient equal to 80%. An increase in Sn concentration increases both the effective band gap energy from 3.2 to 4.01eV and the photoluminescence intensity peak assigned defects to SnO2. The films electrical characterization indicated that films are resistive. Their resistivities vary between 1.2×102 and 3.3×104(Ωcm). The higher resistivity is measured in film deposited with a ratio R equal to 50%.

Nanostructure and magnetic properties of chromium-doped Fe 3B-Nd 2Fe 14B exchange-coupled permanent magnets

Magnetic properties of Nd 4.5Fe 77 − x Cr x B 18.5 and results from high-resolution scanning transmission microscopy (HRSTEM) analysis of Nd 4.5Fe 77B 18.5 and Cr-doped Nd 5.5Fe 71Cr 5B 18.5 nanocomposite permanent magnets are reported. The magnets were prepared from amorphous alloys via a crystallization heat treatment. With increasing Cr content, the intrinsic coercivity ( H cJ) increased and the remanence ( B r) decreased considerably. The average grain size of crystallites was approximately 20 nm and found to be smaller in the Cr-doped sample than in the non-doped one. Two types of regions with the Fe/Nd atomic ratio of approximately 7 were detected by HRSTEM; some regions contain Cr and others do not. Presence of grains of the non-magnetic Nd 1.1Fe 4B 4 phase with negligible Cr contents were also revealed in both Nd 4.5Fe 77B 18.5 and Nd 5.5Fe 71Cr 5B 18.5 samples. The experimental results suggest that, in Cr-doped Nd-Fe-B nanocomposite magnets, Cr is concentrated in Fe and/or Fe x B phases and depleted in the Nd 1.1Fe 4B 4 and some of Nd 2Fe 14B phases after crystallization. The increase in H cJ probably originates from depression of intergrain exchange couplings through Cr concentrated in the soft magnetic phases.