A.Jagadeesh*, Sai Shiv Narayan, T. Mimani Rattan, Saikiran Adithya, K. Venkataramaniah. Sri Sathya Sai Institute of Higher Learning, Prashanti Nilayam, A.P. Pin:515134.
ABSTRACT
INTRODUCTION
RESULTS
Sodium doped nano vanadium pentoxide (V2O5) is synthesized by simple one step synthesis of solution combustion method using citric acid as surfactant. Electrical conductivity measured using Van der pauw four probe method showed enhancement in conductivity with increase in doping concentration.
• Infrared detectors are of great importance in commercial applications due to their low power consumption and low costs. Of these, the micro bolometer types of thermal detectors are the most popular ones.
Electrical :
1.3 wt. % Na doped nano V2O5 showed better temperature coefficient of resistance compare to the undoped nano V2O5.These samples are further characterized by XRD, TEM, DSC and FESEM. Most of the particles are in the range of 200 nm and the sample is crystalline in nature. XRD findings showed an extra peak corresponds to the sodium vanadate phase. DSC analysis of these samples showed that the difference between melting and crystallization temperature is more in 1.3 wt. % Na doped nano V2O5 compare to the undoped nano V2O5.
These characteristics of sodium doped nano V2O5 by solution combustion method is being evaluated for its Thermoelectric Figure of Merit measurements.
• V2O5 is a suitable bolometer active material because of its combination of high TCR (Temperature Coefficient of Resistance), good IR absorption characteristics, and low 1/f noise. • Low resistance and high TCR are essential for a bolometer sensitive material.
• Synthesized Sodium doped vanadium shows better TCR (- 2.51 %) and high conductivity (450 Ω-cm) at the room temperature. • Conductivity of these samples increases with doping concentration and the value increasing 10 times at 300C and 100 times at 1200C compare to undoped vanadium.
Fig.1 Resistivity Vs Temperature plot for Na doped V2O5 samples & TCR values of undoped and 1.35 wt.% Na V2O5.
• The synthesis of V2O5 is a challenge, as it invariably forms a mixture of various phases of VOx or V2Ox either by physical or chemical route. • In this method we synthesized sodium doped nano V2O5 by a simple one step solution combustion method using citric acid as surfactant.
DISCUSSION
Fig.2 Hysteresis plot of undoped and 1.35 wt.% Na V2O5.
Thermal (DSC):
METHODS AND MATERIALS Solution Combustion synthesis:
• Hysteresis loss of 1.35 Wt.% Na V2O5 is less compare to the undoped sample. • XRD shows an extra peak in 1.35 wt.% Na V2O5 sample indicative of sodium vanadate phase. • Thermal analysis shows 1.35 Wt.% Na V2O5 has higher melting point than undoped sample due to dopant sodium. • The difference between melting and crystallization temperature is also less i.e. 98 when compare to the undoped V2O5 i.e.157 which is an indicative of sodium vanadate phase in the sample.
• Reduction in particle size to ~220nm is observed when the combustion is carried out in the presence of citric acid as surfactant.
CONCLUSIONS
• Breaking down process • Basic components are fuel, oxidizer and Temperature.
REACTION: Fig.3 DSC plot of undoped and 1.35 wt.% Na V2O5.
The results indicate that the sodium doped crystalline nano V2O5 can be achieved in this route. And TCR value for 1.35 wt.% Na V2O5 increased to -2.51 % K−1 with resistivity 450 Ω-cm at the room temperature.
2 NH4VO3 + 2 C2H5NO2 + 12 NH4NO3
XRD: MNO3/M2O3 M/V2O5+33 H2+4 CO2+14 N2. Where M = NaNO3.
Finally the sample showed high TCR and low resistivity compare to the commercial V2O5 which indicates 1.35 Wt.% Na V2O5 is a promising agent for micro bolometers and other thermo electric applications.
ACKNOWLEDGEMENTS
Fig.4 XRD shows an extra peak in 1.35 wt.% Na V2O5 sample indicative of sodium vanadate phase.
CONTACT
FESEM & TEM :
A.Jagadeesh Sri Sathya Sai Institute of Higher Learning, Prashanti Nilayam. Email:
[email protected]
Authors express their gratitude to the founder chancellor of SSSIHL, Sri Sathya Sai Baba, for his constant support and lab facilities.
REFERENCES 1. Zerov VY, Kulikov VY et.al. Vanadium oxide films with improved characteristics for IR micro bolometric matrices. Tech Phys Lett 2001;27:378–80.
Electrical measurements were done by four probe method in Vander Pauw configuration using Keithley 2400 source meter as a function of temperature in the range of 20-1200C. These samples are further characterized by XRD, TEM, DSC and FESEM.
2. A.Jagadeesh,T.Mimani Rattan et.al. Instant one step synthesis of crystalline nano V2O5 by solution combustion method showing enhanced negative temperature coefficient of resistance. Materials Letters 121 (2014) 133–136. Fig.5 FESEM of Combustion sample shows layered structure nano V2O5 and TEM analysis shows that the sample is crystalline in nature.
