Rathinam Vasudevan - Academia.edu (original) (raw)

Papers by Rathinam Vasudevan

Advanced Materials Research, 2012

The Gd substituted BaCe0.8Y0.1O3-δ nanocomposites were prepared by a modified Pechini route and t... more The Gd substituted BaCe0.8Y0.1O3-δ nanocomposites were prepared by a modified Pechini route and then the prepared material was subjected to conventional sintering at 1400°C. The powder XRD results show that the material exhibit orthorhombic crystalline structure and the mean particle size were calculated to be ~40 nm. SEM micrographs indicate that the particle sizes were observed in the nanometer range with dense microstructure, which leads to increase in the densification of the material. FT-IR result confirms the presence of metal bondings in the material. DTA peaks observed at 725°C and 880°C show the crystallization of the material and the corresponding weight loss was recorded in the TG spectrum. I-V & I-P results show that the maximum open cell voltage (OCV) was measured at 1.1V and the maximum power density of about 801mWcm2 was observed which may be due to the substitution of Gd ions into the BaCeYO3 sites showing an improved electrochemical performance of IT-SOFC electrolytes.

Journal of Materials Science: Materials in Electronics, 2013

ABSTRACT BaTiO3 nanoparticles were prepared by high energy ball milling and subjected to conventi... more ABSTRACT BaTiO3 nanoparticles were prepared by high energy ball milling and subjected to conventional and microwave post sintering at 1,000 °C. From the powder X-ray diffraction results, the synthesized material exhibits strong tetragonality with large c/a ratio. Scanning electron microscope results show the formation of tetragonal shaped BaTiO3 crystals in the nanometer scale and a significant reduction in the particle size for the microwave sintered sample. The reduced d-spacing of 1.741 Å with high crystallinity for the microwave sintered material is revealed by high resolution transmission electron microscopy analysis. Ultraviolet–visible spectroscopy studies confirm the higher optical band gap (Eg) of 4.157 eV for the microwave sintered sample. Microwave sintered sample shows a very high dielectric constant of εr = 4,445 with a low dielectric loss as tan δ = 0.0961. Microwave sintered sample exhibit a high polarization maximum of 73 μC/mm2 with reduced coercivity to be 0.293 kV/mm.

Ceramics International, 2013

ABSTRACT Zirconia toughened alumina (ZTA) nanocomposites with different zirconia contents (5-20 m... more ABSTRACT Zirconia toughened alumina (ZTA) nanocomposites with different zirconia contents (5-20 mol%) were prepared by the sol-gel method. The prepared composites were sintered at 1300 °C by both conventional and microwave techniques. The crystallinity, average grain size, microstructure and densification of the samples prepared by conventional and microwave sintering methods were compared. X-ray diffraction analysis shows that the microwave sintered samples possess higher tetragonality and also exhibit reduced particle size compared to conventional sintering. HR-SEM surface micrograph reveals that the microwave sintered samples have homogeneous particle size distribution with less degree of porosity. TEM analysis confirms uniform distribution of particles with an average particle size of 20 nm for the microwave sintered sample. SAED pattern reveals that the microwave sintered samples possess improved crystallinity compared to conventional sintered samples. The apparent porosity and density of ZTA nanocomposites measured for different zirconia contents show that the densification of 97% could be achieved for the microwave sintered samples with higher content of zirconium.

Journal of Alloys and Compounds, 2022

Partial replacement of Sn with Ag is an effective method to optimize the thermoelectric performan... more Partial replacement of Sn with Ag is an effective method to optimize the thermoelectric performance of SnSe compounds. However, this approach can easily introduce the AgSnSe2 secondary phase due to the limited solubility of Ag in SnSe. This secondary phase is considered to play positive effects on thermoelectric performance all the way in the previous studies. However, its exact influences on the sample’s properties remain ambiguous. Herein, we report a comprehensive study on the crystal structures and the effects of Ag dopant in SnSe polycrystals. Firstly, neutron powder diffraction measurements demonstrate a sudden phase transition nature at 775 K. In addition, we observe a strong competition between the influences from Ag dopant and AgSnSe2 secondary phase. It finds that the precipitation of AgSnSe2 would deplete the carrier concentration and scatter the mobile carriers. Its appearance in the SnSe matrix also suppresses the lattice thermal conductivity, although lower Ag doping content raises the thermal transport properties. This study
sheds new light on the understanding of the thermoelectric properties in SnSe polycrystals and is expected to guide further optimization of transport properties.

Advanced Materials Research, 2012

The Gd substituted BaCe0.8Y0.1O3-δ nanocomposites were prepared by a modified Pechini route and t... more The Gd substituted BaCe0.8Y0.1O3-δ nanocomposites were prepared by a modified Pechini route and then the prepared material was subjected to conventional sintering at 1400°C. The powder XRD results show that the material exhibit orthorhombic crystalline structure and the mean particle size were calculated to be ~40 nm. SEM micrographs indicate that the particle sizes were observed in the nanometer range with dense microstructure, which leads to increase in the densification of the material. FT-IR result confirms the presence of metal bondings in the material. DTA peaks observed at 725°C and 880°C show the crystallization of the material and the corresponding weight loss was recorded in the TG spectrum. I-V & I-P results show that the maximum open cell voltage (OCV) was measured at 1.1V and the maximum power density of about 801mWcm2 was observed which may be due to the substitution of Gd ions into the BaCeYO3 sites showing an improved electrochemical performance of IT-SOFC electrolytes.

Journal of Materials Science: Materials in Electronics, 2013

ABSTRACT BaTiO3 nanoparticles were prepared by high energy ball milling and subjected to conventi... more ABSTRACT BaTiO3 nanoparticles were prepared by high energy ball milling and subjected to conventional and microwave post sintering at 1,000 °C. From the powder X-ray diffraction results, the synthesized material exhibits strong tetragonality with large c/a ratio. Scanning electron microscope results show the formation of tetragonal shaped BaTiO3 crystals in the nanometer scale and a significant reduction in the particle size for the microwave sintered sample. The reduced d-spacing of 1.741 Å with high crystallinity for the microwave sintered material is revealed by high resolution transmission electron microscopy analysis. Ultraviolet–visible spectroscopy studies confirm the higher optical band gap (Eg) of 4.157 eV for the microwave sintered sample. Microwave sintered sample shows a very high dielectric constant of εr = 4,445 with a low dielectric loss as tan δ = 0.0961. Microwave sintered sample exhibit a high polarization maximum of 73 μC/mm2 with reduced coercivity to be 0.293 kV/mm.

Ceramics International, 2013

ABSTRACT Zirconia toughened alumina (ZTA) nanocomposites with different zirconia contents (5-20 m... more ABSTRACT Zirconia toughened alumina (ZTA) nanocomposites with different zirconia contents (5-20 mol%) were prepared by the sol-gel method. The prepared composites were sintered at 1300 °C by both conventional and microwave techniques. The crystallinity, average grain size, microstructure and densification of the samples prepared by conventional and microwave sintering methods were compared. X-ray diffraction analysis shows that the microwave sintered samples possess higher tetragonality and also exhibit reduced particle size compared to conventional sintering. HR-SEM surface micrograph reveals that the microwave sintered samples have homogeneous particle size distribution with less degree of porosity. TEM analysis confirms uniform distribution of particles with an average particle size of 20 nm for the microwave sintered sample. SAED pattern reveals that the microwave sintered samples possess improved crystallinity compared to conventional sintered samples. The apparent porosity and density of ZTA nanocomposites measured for different zirconia contents show that the densification of 97% could be achieved for the microwave sintered samples with higher content of zirconium.

Journal of Alloys and Compounds, 2022

Partial replacement of Sn with Ag is an effective method to optimize the thermoelectric performan... more Partial replacement of Sn with Ag is an effective method to optimize the thermoelectric performance of SnSe compounds. However, this approach can easily introduce the AgSnSe2 secondary phase due to the limited solubility of Ag in SnSe. This secondary phase is considered to play positive effects on thermoelectric performance all the way in the previous studies. However, its exact influences on the sample’s properties remain ambiguous. Herein, we report a comprehensive study on the crystal structures and the effects of Ag dopant in SnSe polycrystals. Firstly, neutron powder diffraction measurements demonstrate a sudden phase transition nature at 775 K. In addition, we observe a strong competition between the influences from Ag dopant and AgSnSe2 secondary phase. It finds that the precipitation of AgSnSe2 would deplete the carrier concentration and scatter the mobile carriers. Its appearance in the SnSe matrix also suppresses the lattice thermal conductivity, although lower Ag doping content raises the thermal transport properties. This study
sheds new light on the understanding of the thermoelectric properties in SnSe polycrystals and is expected to guide further optimization of transport properties.