55 research outputs found
Understanding a philosophical text. The problem of “meaning” in Jayanta’s Nyāyamañjarī, Book 5
No full textThe authors make an attempt to comparatively analyse some stances of the Old Indian philosophy of language, exemplified by the Medieval Indian author Jayanta, along with the Western tradition of the analytical philosophy of language, and to highlight the differences as well as the similarities
Studies On Pure And Modified Antiferroelectric PbZrO3 Thin Films
No full textMetal oxides crystallized in perovskite structure are generally modified in two different ways. According to the general structural formula ABO3, the two ways are A-site modification and B-site modification. The primary significance of perovskite metal oxides rests on their importance in electronic devices. A particular class of perovskites, namely Lead Zirconate or modified Lead Zirconate has received a special attention because of their unique antiferroelectricity and various applications in devices. Among the other modifications, A-site modification of PbZrO3 by La is rare and not much explored. Chapter 1 describes various applications of antiferroelectric thin films along with the synthesis and characterization of pure and La modified PbZrO3, which are relevant to the work presented in this thesis.
Sol-gel processing and spin coating technique to deposit solid oxide thin films are well known for their low cost of deposition as well as for their ability to achieve better stoichiometric chemical composition. Common crack formation problem of sol-gel grown films can be prevented by ‘drying control chemical adhesive’ like polyvinylpyrrolidone (PVP). Heat treatment of sol-gel derived thin films is generally determined by TGA and DTA. Crystalline phase of deposited solid thin films is determined by XRD whereas effect of modification can be ascertained by XRD peak assignment and relative crystalline peak shifting. Sol-gel grown film thickness is measured by common cross sectional SEM whereas AFM can detail the surface morphology. Chapter 2 summarizes the deposition and characterization of pure and La modified PbZrO3 thin films.
Any nonmetal, which is insulator, is dielectric material and show dielectric dispersion in a frequency domain of low field alternative current. Among the most common feature of dielectric dispersion, Maxwell – Wagner type dispersion is well known. Similar kind of dielectric dispersion, named Maxwell – Wagner like dispersion, can be observed while the equivalent circuit consists of parallel G – C along with a series R. Universal power law of ac conductivity is the deciding factor to distinguish the nature of dispersion. Structural phase transition can be determined by dielectric response and it is widely known as dielectric phase transition. Effect of La modification on dielectric phase transition of PbZrO3 thin films depends on stabilization or destabilization of antiferroelectricity. Maximum dielectric constants of pure and modified PbZrO3 thin films depend on the crystallographic orientations of the growth. Chapter 3 presents dielectric properties of pure and La modified PbZrO3 thin films and these properties are correlated to the stabilization or destabilization of antiferroelectricity, relative integrated intensity of (202)O film orientation and trapped electron charge due to oxygen vacancies.
Charge storage property of a capacitor is determined by the polarization of the capacitor on application of electric field whereas field dependent integrated area of polarization on withdrawal of electric field determines the recoverable capacitive energy storage. Among the three kinds of capacitors like linear or paraelectric, ferroelectric and antiferroelectric capacitors, antiferroelectric capacitor is known to be best for their ability to store huge amount of recoverable energy. The recoverable energy in antiferroelectrics can be increased by increasing squareness of the P – E hysteresis loop, applicable electric field, polarization or by the all possible combinations of them. Chapter 4 describes the correlation of relative integrated intensity of (202)O [RI(202)O] with critical applied electric field of P – E saturation to provide enhanced squareness of the hysteresis loops. This chapter also describes the variation of charge and recoverable energy storage properties with respect to RI(202)O.
Like magnetocaloric effect, electrocaloric effect is capable to alter the temperature of a system by adiabatic polarization or depolarization. From the Maxwell’s relation of thermodynamics, assuming, (∂p ) = (∂s )electrocaloric effect can be calculated from temperature dependent polarization value of a paraelectric, ferroelectric or an antiferroelectric. Chapter 5 presents the electrocaloric effect of pure and La modified PbZrO3 thin films.
Summary of present study and discussion have been delineated in Chapter 6 along with the future work which can give more insight into the understanding of antiferroelectric PbZrO3 thin films with respect to Pb and Zr site modification and with respect to different electrodes.
(For formulas pl see the pdf file of the thesis
Enhancement of charge and energy storage in sol-gel derived pure and La-modified PbZrO<SUB>3</SUB> thin films
No full textAntiferroelectric lanthanum-modified PbZrO3 thin films with La contents between 0 and 6 at.% have been deposited on Pt(111)/Ti/SiO2/Si substrate by sol-gel route. On the extent of La-modification, maximum polarization (Pmax) and recoverable energy density (W) have been enhanced followed by their subsequent reduction. A maximum Pmax (~0.54 C/m2 at ~60 MV/m) as well as a maximum W (~14.9 J/cc at ~60 MV/m) have been achieved on 5% La modification. Both Pmax and W have been found to be strongly dependent on La-induced crystallographic orientations
Dielectric properties of (110) oriented PbZrO<SUB>3</SUB> and La-modified PbZrO<SUB>3</SUB> thin films grown by sol-gel process on Pt(111)/Ti/SiO<SUB>2</SUB>/Si substrate
No full textHighly (110) preferred orientated antiferroelectric PbZrO3 (PZ) and La-modified PZ thin films have been fabricated on Pt/Ti/SiO2/Si substrates using sol-gel process. Dielectric properties, electric field induced ferroelectric polarization, and the temperature dependence of the dielectric response have been explored as a function of composition. The Tc has been observed to decrease by ~17° C per 1 mol% of La doping. Double hysteresis loops were seen with zero remnant polarization and with coercive fields in between 176 and 193 kV/cm at 80° C for antiferroelectric to ferroelectric phase transformation. These slim loops have been explained by the high orientation of the films along the polar direction of the antiparallel dipoles of a tetragonal primitive cell and by the strong electrostatic interaction between La ions and oxygen ions in an ABO3 perovskite unit cell. High quality films exhibited very low loss factor less than 0.015 at room temperature and pure PZ; 1 and 2 mol% La doped PZs have shown the room temperature dielectric constant of 135, 219, and 142 at the frequency of 10 kHz. The passive layer effects in these films have been explained by Curie constants and Curie temperatures. The ac conductivity and the corresponding Arrhenius plots have been shown and explained in terms of doping effect and electrode resistance
Enhancement of charge and energy storage in sol-gel derived pure and La-modified thin films
No full textAntiferroelectric lanthanum-modified thin films with La contents between 0 and 6 at. % have been deposited on Pt(111) substrate by sol-gel route. On the extent of La-modification, maximum polarization and recoverable energy density (W) have been enhanced followed by their subsequent reduction. A maximum at as well as a maximum W at have been achieved on 5% La modification. Both and W have been found to be strongly dependent on La-induced crystallographic orientations
Electrocaloric effect in antiferroelectric PbZrO3 thin films
No full textAntiferroelectric PbZrO3 thin films have been deposited on Pt(111)/Ti/SiO2/Si substrate by polymer modified sol-gel route. Temperature dependent P -E hysteresis loops have been measured at 51 MV/m within a temperature range of 40 °C to 330 °C. The maximum electrocaloric effect 0.224 × 10-6 K mV-1 has been observed near the dielectric phase transition temperature (235 °C) of the thin films. The electrocaloric effect and its strong temperature dependence have been attributed to nearly first-order phase transition
Dielectric properties of (110) oriented PbZrO3 and La-modified PbZrO3 thin films grown by sol-gel process on Pt(111)/Ti/SiO2/Si substrate
No full textHighly (110) preferred orientated antiferroelectric PbZrO3 (PZ) and La-modified PZ thin films have been fabricated on Pt/Ti/SiO2/Si substrates using sol-gel process. Dielectric properties, electric field induced ferroelectric polarization, and the temperature dependence of the dielectric response have been explored as a function of composition. The Tc has been observed to decrease by ∼ 17 °C per 1 mol % of La doping. Double hysteresis loops were seen with zero remnant polarization and with coercive fields in between 176 and 193 kV/cm at 80 °C for antiferroelectric to ferroelectric phase transformation. These slim loops have been explained by the high orientation of the films along the polar direction of the antiparallel dipoles of a tetragonal primitive cell and by the strong electrostatic interaction between La ions and oxygen ions in an ABO3 perovskite unit cell. High quality films exhibited very low loss factor less than 0.015 at room temperature and pure PZ; 1 and 2 mol % La doped PZs have shown the room temperature dielectric constant of 135, 219, and 142 at the frequency of 10 kHz. The passive layer effects in these films have been explained by Curie constants and Curie temperatures. The ac conductivity and the corresponding Arrhenius plots have been shown and explained in terms of doping effect and electrode resistance
Dielectric properties of (110) oriented and La-modified thin films grown by sol-gel process on substrate
No full textHighly 110 preferred orientated antiferroelectric (PZ) and La-modified PZ thin films have been fabricated on substrates using sol-gel process. Dielectric properties, electric field induced ferroelectric polarization, and the temperature dependence of the dielectric response have been explored as a function of composition. The has been observed to decrease by \sim 17 °C per 1 mol % of La doping. Double hysteresis loops were seen with zero remnant polarization and with coercive fields in between 176 and 193 kV/cm at 80 °C for antiferroelectric to ferroelectric phase transformation. These slim loops have been explained by the high orientation of the films along the polar direction of the antiparallel dipoles of a tetragonal primitive cell and by the strong electrostatic interaction between La ions and oxygen ions in an perovskite unit cell. High quality films exhibited very low loss factor less than 0.015 at room temperature and pure PZ; 1 and 2 mol % La doped PZs have shown the room temperature dielectric constant of 135, 219, and 142 at the frequency of 10 kHz. The passive layer effects in these films have been explained by Curie constants and Curie temperatures. The ac conductivity and the corresponding Arrhenius plots have been shown and explained in terms of doping effect and electrode resistance
Electrocaloric effect in antiferroelectric PbZrO<SUB>3</SUB> thin films
No full textAntiferroelectric PbZrO3 thin films have been deposited on Pt(111)/Ti/SiO2/Si substrate by polymer modified sol-gel route. Temperature dependent P -E hysteresis loops have been measured at 51 MV/m within a temperature range of 40 °C to 330 °C. The maximum electrocaloric effect ~0.224 × 10-6 K mV-1 has been observed near the dielectric phase transition temperature (235 °C) of the thin films. The electrocaloric effect and its strong temperature dependence have been attributed to nearly first-order phase transition
Wide Ranged La Modification in CCTO Ceramics Through Sol-Gel: Effect on Microstructure and Dielectric Properties
No full textSol-Gel method was employed to synthesize pure and wide ranged La-modified CaCu3Ti4O12 ceramics using mixed acetate-nitrate-alcoxide individual metal-ion precursors. SEM pictures revealed that grain size monotonously decreases with the extent of La incorporation. All the prepared ceramics manifested dielectric constant in the range similar to 10(3)-10(4). Dielectric loss was found to decrease with La incorporation and got optimized for 20% La3+ while retaining its high dielectric constant which may be industrially important. Room temperature Impedance spectroscopy suggested that decrease in grain resistance is responsible for reduction in dielectric loss according to Internal Barrier Layer Capacitor (IBLC) model
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