• Ali Nemati

Articles written in Bulletin of Materials Science

• Effect of working pressure and annealing temperature on microstructure and surface chemical composition of barium strontium titanate films grown by pulsed laser deposition

Barium strontium titanate (BST, Ba1−𝑥Sr𝑥TiO3) thin films have been extensively used in many dielectric devices such as dynamic random access memories (DRAMs). To optimize its characteristics, a microstructural control is essential. In this paper, Ba0.6Sr0.4TiO3 thin film has been deposited on the SiO2/Si substrate by the pulsed laser deposition (PLD) technique at three different oxygen working pressures of 100, 220 and 350 mTorr. Then the deposited thin films at 100 mTorr oxygen pressure were annealed for 50 min in oxygen ambient at three different temperatures: 650, 720 and 800°C. The effect of oxygen working pressure during laser ablation and thermal treatment on the films was investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis methods. X-ray photoelectron spectroscopy analysis was used to determine the surface chemical composition of the samples. The results indicate that the deposited BST film at low working pressure (100 mTorr) in PLD chamber shows a lower surface roughness than other working pressures (220 and 350 mTorr). The as-deposited films show an amorphous structure and would turn into polycrystalline structure at annealing temperature above 650°C. Increase of temperature would cause the formation of cubic and per-ovskite phases, improvement in crystalline peaks and also result in the decomposition of BST at high temperature (above 800°C). In addition, rising of temperature leads to the increase in size of grains and clusters. Therefore more roughness was found at higher temperatures as a result of a more heterogeneous growth and less tensions.

• Influence of preparation procedure and ferric oxide nanoparticles addition on transport properties of homogeneous cation-exchange SPPO/SPVC membrane

Homogeneous cation-exchange membranes were prepared through evaporation and phase inversion methodsusing sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) and sulfonated polyvinylchloride as binders. The effectof polymers blend’s ratio and preparation method on structure and electrochemical properties of the prepared membraneswere evaluated. The microstructures of the membranes were investigated by scanning electron microscopy (SEM) andthe sulfonation of polyvinylchloride was confirmed by elemental analyses. Moreover, the membranes performance wasevaluated by ion-exchange capacity (IEC), fixed ion concentration, membrane potential, transport number, permselectivity,areal resistance, ionic permeability, flux of ions, current efficiency, membrane oxidative stability, mechanical properties andwater content tests. The results indicated that IEC and water content were affected by the SPPO content and microstructuresof the membranes. The results showed increased efficiency and suitable electrochemical properties for membranes preparedby the evaporation method in comparison with others. Also, Fe$_2$O$_3$ nanoparticles were synthesized at room temperature by a simple sonochemical reaction between ferric chloride and NaOH. The results revealed that the addition of different amounts of Fe$_2$O$_3$ nanoparticles to the polymeric matrix could affect the hydrophilicity and transport properties of ion-exchange membranes.

• Gel combustion synthesis of fluorine-doped tin oxide and its characteristics: applying D-optimal factorial design of experiment

Fluorine-doped tin oxide (FTO) nano-powders were synthesized by a gel combustion method. To analyse the effect of processing factors and their interactions and to achieve an equation for nano-powder particle size in termsof code factors, D-optimal factorial design was used. Stannous chloride penta-hydride, ammonium fluoride and citric acid were used to synthesize the FTO nano-powders. The structure, morphology and composition of the synthesized powders were characterized by X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The results revealed the formation of homogenous FTO nano-powders with an average particle size of 20 nm and equiaxed morphology in the concentration of precursor 0.2, citric acid to precursor molar ratio of 1 and pH of 0.5. The average particle size increased as the concentration of the precursor, citric acid to precursor molar ratio and pH increased from 0.2 to 1, 1 to 3 and 0.5 to 3, respectively. Citric acid to precursor molar ratio, concentration of the precursor and the pH had the most significant effect on the synthesis of the FTO nano-powders, respectively.

• # Bulletin of Materials Science

Volume 44, 2021
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020