Dielectric Loss Studies and Electronic Properties of Mandelic Acid

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AASCIT Journal of Physics 2015; 1(1): 6-10 Published online March 30, 2015 (http://www.aascit.org/journal/physics) Dielectric Loss Studies and Electronic Properties of Mandelic Acid S. Usha 1, *, K.

Subramaniam 2, Charles Kanakam Christopher 3 1 Department of Chemistry, Sri Sairam Engineering College, Chennai, India 2 Department of Physics, Sri Sairam Engineering College, Chennai, India 3

Usha) Keywords Dielectric Loss, Dielectric Constant, Quality Factor, Mandelic Acid, Conductivity, Phase Angle Received: February 12, 2015 Revised: March 16, 2015 Accepted: March 17, 2015 Citation S.

1 AASCIT Journal of Physics 2015; 1(1): 6-10 Published online March 30, 2015 ( Dielectric Loss Studies and Electronic Properties of Mandelic Acid S. Usha 1, *, K. Selvarani 2, T. K. Subramaniam 2, Charles Kanakam Christopher 3 1 Department of Chemistry, Sri Sairam Engineering College, Chennai, India 2 Department of Physics, Sri Sairam Engineering College, Chennai, India 3 Department of Chemistry, Presidency College, Chennai, India address usha.che@sairam.edu.in (S. Usha) Keywords Dielectric Loss, Dielectric Constant, Quality Factor, Mandelic Acid, Conductivity, Phase Angle Received: February 12, 2015 Revised: March 16, 2015 Accepted: March 17, 2015 Citation S. Usha, K. Selvarani, T. K. Subramaniam, Charles Kanakam Christopher. Dielectric Loss Studies and Electronic Properties of Mandelic Acid. AASCIT Journal of Physics. Vol. 1, No. 1, 2015, pp Abstract Electrical stability is essential for a successful commercialization of organic semiconductor devices. The polarisability of the bulk of organic semiconductors depends on materials. Organic solids such as benzimidazole, aminopyridine, copper phthalocyanine - polyaniline in polyurethane are good dielectric materials which can replace traditional ceramic semiconductors due to their low dielectric loss, high dielectric constant and good electrical conductivity property at higher frequencies. The dielectric study of non-centerosymmetric organic molecule like mandelic acid (MA) having higher polarisability is studied for the first time at various temperatures. Comparative graphs are plotted from 50 Hz 5 MHz log f values against, capacitance in parallel, conductivity, dielectric loss, dielectric constant, phase angle - loss tangent, quality factor, resistance in series, resistance in parallel, for 40 C, 60 C, 80 C and 100 C respectively. The title compound shows metallic property, minimum dielectric loss, high dielectric constant and good breakdown strength at higher frequencies, at various temperatures and it can be used as a good dielectric material at higher frequencies. Solid organic dielectric material MA can be used as a suitable dielectric material till 80 C in device applications like disc capacitors, sensors and photovoltaic cell. 1. Introduction A dielectric material is an electrical insulator that can be polarized by an applied electric field. Dielectrics are important for explaining various phenomena in electronics, optics, and solid-state physics [1]. The complicated electronic and molecular structural properties of organic materials, a distorted region around the charge carrier can be created by several different microscopic mechanisms like polarisation of the individual molecules, the deformation of the molecular lattice, and the distortion of the conformation molecules. The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. The band gap in the insulators is narrowed by the application of voltage (the breakdown voltage) which leads the excitation of electrons to the conduction band, thus the dielectric will lose its insulating properties. Organic Electronics is a new field of electronics in which the structures that are used are based on organic materials: dielectric, conductive or semiconductor polymers or small organic molecules deposited mainly on flexible substrates [2]. In simple organic molecules and semi organic

2 AASCIT Journal of Physics 2015; 1(1): molecules like aminopyridine, benzimidazole, copper phthalocyanine oligomer and conductive polyaniline within polyurethane ionic polarisability present in the molecules are helping the usage of them as dielectric materials in device applications[3-5]. MA is an aromatic α- hydroxy acid with the molecular formula C 6 H 5 CH (OH) COOH. It is a white crystalline solid, soluble in water, polar organic solvents. Its melting point is 119 C and polarisability is MA molecule is noncenterosymmetric. Ionic conductivity of MA in solution is studied [6], but the solid material dielectric study is carried out for the first time. Organic solid material MA shows high dielectric constant, low dielectric loss at higher frequencies can be used in capacitors [7] and other electrical devices due to their good conductivity property [8],act as dielectric material up to certain temperature [9] and breakdown occurs [10,12]. 2. Experimental Techniques MA free from moisture content is purchased from Alfa Aesar (99% pure, dl mixture). The crystalline white powder is made into pellet with KBr under a pressure of ~ N/m 2. The pellet having thickness of 5.77 mm and diameter of mm is placed in the sample holder designed to minimize stray capacitance to simulate a disc capacitor. A programmable automatic RLC bridge, model HIOKI Hitester is used to measure the capacitance in parallel Cp, resistance in series R s, resistance in parallel Rp, conductance G[13], phase angle- the loss tangent tan δ phase [14-20], power factor Q, dielectric loss D, directly in the range of frequencies from 50 Hz to 5 MHz. The temperature of the sample is measured by a thermocouple obtained by maintaining four different temperatures 40 C, 60 C, 80 C and 100 C respectively. A comparative graph is plotted for each parameter between log frequency values and each parameter four different temperature values respectively. Calculated, plotted graphs for the dielectric constant and conductivity of the title compound with respect to temperatures. Table 1. Comparison of capacitance in parallel for MA log f 40 C 60 C 80 C 100 C E E E E E E E E E E E E E E E E E E E E E E E E-11 Fig. 1. Variation of capacitance in parallel with temperature for MA Table 2. Comparison of dielectric constant for MA Fig. 2. Variation of capacitance in parallel with temperature for MA Table 3. Comparison of conductance for MA E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-05

3 8 S. Usha et al.: Dielectric Loss Studies and Electronic Properties of Mandelic Acid Fig. 5. Variation of resistance in parallel with temperature for MA Fig. 3. Variation of conductance with temperature for MA Table 4. Comparison of conductivity for MA Table 6. Comparison of resistance in series for MA Fig. 6. Variation of resistance in series with temperature for MA Table 7. Comparison of loss tangent for MA Fig. 4. Variation of conductivity with temperature for MA log f 40 C 60 C 80 C 100 C Table 5. Comparison of resistance in parallel for MA log f 40 C 60 C 80 C 100 C E E E E E E E E E E E E E E Fig. 7. Variation of phase angle with temperature for MA

4 AASCIT Journal of Physics 2015; 1(1): Table 8. Comparison of quality factor for MA Fig. 8. Variation of quality factor with temperature for MA Table 9. Comparison of dielectric loss for MA Result and Discussion Small organic molecules amino pyridine, benzimidazole and polymer semi-organic materials are used as dielectric materials in traditional capacitors as substituent for ceramic materials The highly polarisable material MA is subjected to dielectric study. At low AC frequencies significant capacitance values are observed for MA connected in parallel. The highest capacitance of the title compound at 80 C shows dielectric breakdown properties is indicated by Fig. 1. The high ionic polarisation of the solid electrolyte MA show high dielectric constant with respect to temperature and frequency is shown by Fig.2. The conductance value remains almost zero at lower frequencies, then the conductance slowly increases for MA and reaches a peak value for 100 C between 0.9 MHz and 3 MHz and the relative intensities of conductance is less for other temperatures is indicated by Fig.3. The increase in temperature and frequency increases conductivity respectively is shown by Fig.4., indicates the metallic behaviour of the title compound. According to Ohm s law temperature is directly proportional to resistance for metals.the title compound shows the increase in resistance of Ω at 80 C is indicated by Fig. 5. and reveals MA can act as a good conductor beyond 80 C when connected in parallel connection, exhibiting dielectric breakdown properties at 80 C. In the measurement of resistance in series of MA, the increase in temperatures decrease the resistance value indicates the metallic behaviour of MA is shown by Fig.6. The thermal energy disrupts the ion dipole interaction which is responsible for polarization at higher temperatures, causing the relaxation of polarization known as δ, or "tan δ", the power loss factor is the dielectric relaxation of the sample. Phase angle is maximum for 60 C indicating current leading the voltage in a dielectric material like MA from Fig. 7. due to impurities present in the sample. The power factor, also known as Q factor, the ratio of its reactance to its resistance at a given frequency, and is a measure of its efficiency. The higher the Q factor of the capacitor, the closer it approaches the behavior of an ideal, lossless, capacitor is shown by Fig.8. and, Q factor reaches the highest value at 80 C. The minimum dielectric loss at higher frequencies with respect to temperature indicates the title compound can act as a good dielectric material till its breakdown strength at 80 C is shown by Fig.9. A good solid dielectric material requires high dielectric constant low dielectric loss, free from gaseous inclusions and moisture, resistance to thermal and chemical detoriation and higher breakdown strength. The title compound satisfies the requirements of dielectric material and it can be used for device applications in simple to super capacitors. Fig. 9. Variation of dielectric loss with temperature for MA

5 10 S. Usha et al.: Dielectric Loss Studies and Electronic Properties of Mandelic Acid 4. Conclusion The electronic and dielectric properties of MA are unique in the presence of AC electric field is reported for the first time. Solid MA exhibits metallic behavior up to 80 C and thereafter dielectric breakdown begins. High dielectric constant, increased conductivity minimum dielectric loss and high breakdown strength with respect to frequency and temperature indicates the suitability of the title compound for device applications. Acknowledgement Authors wish to thank Physics Department, Loyola College, Chennai, for their technical support and staff members of Humanities and Science of Sri Sairam Engineering College, Chennai, for their motivation and guidance. References [1] Juliusz Sworakowski, Annu. Rep. Prog. Chem. Sec. C, Vol. 99, pp , [2] F. J. Burger, Dielectric Breakdown in Electrolytic Capacitors, J. Electrochem Soc., Vol. 118, pp , [3] T.A rumanayagam, P. Murugakoothan, Optical conductivity and dielectric response of an organic aminopyridine NLO single crystal J. Minerals & Materials Characterisation and engineering.,vol 10, No.13, pp , [4] S. Rajasekar et al, Growth and dielectric studies of benzimidazole: A novel organic NLO material, Arch. App. Sci. Res. Vol. 4, pp , [5] Cheng Huang and Q. M. Zhang, All-organic dielectricpercolative three-component composite mateials with high electro mechanical response, Applied Physics Letters Vol 84,No 22, pp , 31 May [6] Laurence E Strong and Daniel Drake, Ionisation of aqueous mandelic acid: Conductance and Thermodynamics, Proceedings of the Indiana Academy of science, , [7] F. Yakuphanoglu, DC and AC conductivity and dielectric properties of the meta lradical compound: Aqua [bis(2- dimethylaminomethyl-4-nitphenolato)]copper(ii), Solid state commun. Vol. 128, pp 63-67, [8] Igor N. Evdokimov, Electrical Conductivity and Dielectric Properties of Solid Asphaltenes, Energy&fuels, Vol. 24, pp , [9] A. M. Saleh, Dielectric response and electric properties of organic semiconducting phthalocyanine thin films, Journal of semiconductors, Vol. 33, pp , [10] J. R. Lucas, High Voltage Engineering pp 27-34, [11] E. Onal, Electronics and Electrical Engineering, Vol. 121, pp 27-32, [12] V. I. Kichigin, Electrical conductivity and IR spectra of molten benzoic acid, Russ. J. Appl. Chemistry, Vol. 84, pp , [13] M. S. Venkatesh, An overview of dielectric properties measuring techniques, Canadian biosystems engineering, Vol. 47, pp , [14] A. A. Hendi, AC Conductivity and Dielectric Measurements of Bulk Tertracyanoquinodimethane, Australian Journal of Basic and Applied Sciences, Vol. 5, pp , [15] M. N. Ravishankar, Comparative study of mechanical, dielectric and electrical properties of solution grown semiorganic NLO crystal glycine with additives-ammonium oxalate, potassium and barium nitrate, Indian J. PureAppl. phys. Vol. 51, pp 55-59, [16] S. Devikala, Conductivity and Dielectric studies of PMMA composites, Chem Sci Trans. Vol. 2, pp 29-34, [17] Chandrakumar Dixit, Dielectric and conductivity studies of nickel nitratehexahydrateni (N03)2 6H20 ferroelectrics, IJEEER, Vol. 3, pp 25-32, [18] M. P. Binitha, Growth, Characterization and Dielectric Property Studies of Zinc Succinate Crystals Grown in Silica Gel Medium, IOSR-JAP, Vol. 2, pp 13-17, [19] M. Jayalakshmi, Simple Capacitors to Supercapacitors An Overview, Int. J. Electrochem. Sci. Vol. 3, pp , 2008.

AASCIT Journal of Chemistry 2015; 2(3): Published online April 20, 2015 (http://www.aascit.org/journal/chemistry)

AASCIT Journal of Chemistry 2015; 2(3): 55-60 Published online April 20, 2015 (http://www.aascit.org/journal/chemistry) Study of Molecular Interactions of Binary Mixture of Mandelic Acid in Different Solvents