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Papers by Ashish Yadav

Research paper thumbnail of Implementation of IEEE 802.15.4 Standard for LR-WPANs and addressing some of the shortcomings of the MAC Layer

Research paper thumbnail of A Review of the Challenges in the Implementation of Next-Generation ZigBee Networking

Iete Technical Review, 2008

One of the key challenges in the implementation of ZigBee networks is the development of algorith... more One of the key challenges in the implementation of ZigBee networks is the development of algorithms which provide autonomous meshing of beacons with minimal or no interference. This feature is out of the scope of current ZigBee capabilities. The energy and bandwidth constraints ...

Research paper thumbnail of Intense red-emitting Y_4Al_2O_9:Eu^3+phosphor with short decay time and high color purity for advanced plasma display panel

Optics Express, 2009

A new phosphor Y 4 Al 2 O 9 :Eu 3+ (YAM:Eu 3+ ) emitting intense monochromatic red at 612 nm unde... more A new phosphor Y 4 Al 2 O 9 :Eu 3+ (YAM:Eu 3+ ) emitting intense monochromatic red at 612 nm under vacuum ultraviolet (VUV) and ultraviolet (UV) excitations has been developed for application in next generation plasma display panels (PDPs). The developed phosphor has better luminescence efficiency, colour purity and shorter decay time than commercial (Y,Gd)BO 3 :Eu 3+ red emitting PDP phosphor. High color purity (x = 0.67, y = 0.32) under VUV excitation with short decay time (1.03 msec) and excellent stability against degradation during PDP panel preparation suggest that YAM:Eu 3+ is a potential candidate for present and future PDPs. Surface coating by SiO 2 further improved phosphor characteristics.

Research paper thumbnail of Enhanced luminescence and degradation resistance in Tb modified Yttrium Borate core–nano silica shell phosphor under UV and VUV excitation

Applied Surface Science, 2011

Composition variation in optimized solid state reaction conditions has been done to achieve inten... more Composition variation in optimized solid state reaction conditions has been done to achieve intense green emission in YTb x BO 3 phosphor under UV and VUV (147 nm resonant Xe*, 172 nm Xe 2 * excimer band) excitation. Inert interface layer created by fabricating a shell of silica nanoparticles over individual phosphor grain protected the phosphor surface from deterioration and oxidation of luminescent ion (Tb 3+ ) thus completely arresting phosphor degradation. At optimum Tb content of 20 mol%, integrated photoluminescence intensity of developed YTb x BO 3 phosphor is four times higher than commercial green YBT. With short decay time of 4 ms, YTb x BO 3 core-nano silica shell green emitting phosphor has great application potential in PDP panel and phosphor coated Xe lamps.

Research paper thumbnail of Role of valence state of dopant (Eu 2+, Eu 3+) and growth environment in luminescence and morphology of SrAl 12O 19 nano- and microcrystals

Materials Chemistry and Physics, 2010

Incorporation of europium luminescent centre in its chosen valence state Eu 2+ or Eu 3+ has been ... more Incorporation of europium luminescent centre in its chosen valence state Eu 2+ or Eu 3+ has been effectively done in the complex strontium hexa aluminate SrAl 12 O 19 by high temperature solid state reaction at regulated environment. Nanocrystalline SrAl 12 O 19 doped with europium in its reduced form Eu 2+ , could be successfully synthesized by controlled autocombustion process from the nitrate salts of precursor components. The charge state of the dopant ion was ascertained from photoluminescence studies which show series of sharp emission lines in 590-710 nm range for Eu 3+ activator whereas broad green emission for Eu 2+ activator. Nanocrystalline SrAl 12 O 19 :Eu showed blue shifted broad green emission characteristic of Eu 2+ 4f5d transition demonstrating the effectiveness of autocombustion process in producing Eu 2+ charge state which usually requires a reducing environment. Intra-band gap excitation of SrAl 12 O 19 between energy levels of rare earth dopant could be tailored effectively to obtain broad excitation transition in near UV/violet region and emission in the visible region. Striking dependence of morphology on valence state of Eu and growth environment was observed which could be explained due to creation of solid state defects in formation of lamellar structure in oxygen-rich environment.

Research paper thumbnail of Implementation of IEEE 802.15.4 Standard for LR-WPANs and addressing some of the shortcomings of the MAC Layer

Research paper thumbnail of A Review of the Challenges in the Implementation of Next-Generation ZigBee Networking

Iete Technical Review, 2008

One of the key challenges in the implementation of ZigBee networks is the development of algorith... more One of the key challenges in the implementation of ZigBee networks is the development of algorithms which provide autonomous meshing of beacons with minimal or no interference. This feature is out of the scope of current ZigBee capabilities. The energy and bandwidth constraints ...

Research paper thumbnail of Intense red-emitting Y_4Al_2O_9:Eu^3+phosphor with short decay time and high color purity for advanced plasma display panel

Optics Express, 2009

A new phosphor Y 4 Al 2 O 9 :Eu 3+ (YAM:Eu 3+ ) emitting intense monochromatic red at 612 nm unde... more A new phosphor Y 4 Al 2 O 9 :Eu 3+ (YAM:Eu 3+ ) emitting intense monochromatic red at 612 nm under vacuum ultraviolet (VUV) and ultraviolet (UV) excitations has been developed for application in next generation plasma display panels (PDPs). The developed phosphor has better luminescence efficiency, colour purity and shorter decay time than commercial (Y,Gd)BO 3 :Eu 3+ red emitting PDP phosphor. High color purity (x = 0.67, y = 0.32) under VUV excitation with short decay time (1.03 msec) and excellent stability against degradation during PDP panel preparation suggest that YAM:Eu 3+ is a potential candidate for present and future PDPs. Surface coating by SiO 2 further improved phosphor characteristics.

Research paper thumbnail of Enhanced luminescence and degradation resistance in Tb modified Yttrium Borate core–nano silica shell phosphor under UV and VUV excitation

Applied Surface Science, 2011

Composition variation in optimized solid state reaction conditions has been done to achieve inten... more Composition variation in optimized solid state reaction conditions has been done to achieve intense green emission in YTb x BO 3 phosphor under UV and VUV (147 nm resonant Xe*, 172 nm Xe 2 * excimer band) excitation. Inert interface layer created by fabricating a shell of silica nanoparticles over individual phosphor grain protected the phosphor surface from deterioration and oxidation of luminescent ion (Tb 3+ ) thus completely arresting phosphor degradation. At optimum Tb content of 20 mol%, integrated photoluminescence intensity of developed YTb x BO 3 phosphor is four times higher than commercial green YBT. With short decay time of 4 ms, YTb x BO 3 core-nano silica shell green emitting phosphor has great application potential in PDP panel and phosphor coated Xe lamps.

Research paper thumbnail of Role of valence state of dopant (Eu 2+, Eu 3+) and growth environment in luminescence and morphology of SrAl 12O 19 nano- and microcrystals

Materials Chemistry and Physics, 2010

Incorporation of europium luminescent centre in its chosen valence state Eu 2+ or Eu 3+ has been ... more Incorporation of europium luminescent centre in its chosen valence state Eu 2+ or Eu 3+ has been effectively done in the complex strontium hexa aluminate SrAl 12 O 19 by high temperature solid state reaction at regulated environment. Nanocrystalline SrAl 12 O 19 doped with europium in its reduced form Eu 2+ , could be successfully synthesized by controlled autocombustion process from the nitrate salts of precursor components. The charge state of the dopant ion was ascertained from photoluminescence studies which show series of sharp emission lines in 590-710 nm range for Eu 3+ activator whereas broad green emission for Eu 2+ activator. Nanocrystalline SrAl 12 O 19 :Eu showed blue shifted broad green emission characteristic of Eu 2+ 4f5d transition demonstrating the effectiveness of autocombustion process in producing Eu 2+ charge state which usually requires a reducing environment. Intra-band gap excitation of SrAl 12 O 19 between energy levels of rare earth dopant could be tailored effectively to obtain broad excitation transition in near UV/violet region and emission in the visible region. Striking dependence of morphology on valence state of Eu and growth environment was observed which could be explained due to creation of solid state defects in formation of lamellar structure in oxygen-rich environment.

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