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 | Resonant frequencies of whispering gallery modes of dielectric resonator
Author : Badnikar, S.L.;Shanmugam, N.;Murthy, V.R.K.
Source : Defence Science Journal ; Vol:51(2) ; 2001 ; pp 189-193
Subject : 681.2 Instrumentation
Keywords : Dielectrics;Dielectric constant
Abstract : The modal spectrum of the whispering gallery modes of dielectric resonator depends mainly on its physical dimensions, dielectric constant, and to a lesser extent, on the environment. This paper carries investigation of the resonant frequencies in dielectric disc utilising the ring resonator model. Results of the structural design parameters are used to generate a nume!ical expression for describing the operational frequencies useful for computer-aided design applications. Theoretical and experimental results are given for resonators of various sizes. |
| | Frequency Dependence of Attenuation Constant of Dielectric Materials
Author : Zadgaonkar, A.S.;Kakkar, S.S.
Source : Defence Science Journal ; Vol:25(1) ; 1975 ; pp 21-24
Subject : 621.38 Electronics
Keywords : Cathode-ray-oscillograph;Dielectric Constant;Electromagnetic Propogating Wave
Abstract : Different dielectric materials have been studied for frequency dependence of attenuation constant. The sensitive cathode ray oscillograph method has been used to evaluate to the dielectric constant and loss factor, and from these attenuation constants have been calculated. The temperature remaining constant, a regular increase has been observed in attenuation constant, at higher frequencies of electro-magnetic propagating wave. |
| | Alumina-based Ceramic Material for High-voltage Ceramic Substrate
Author : Sangawar, S.R.;Kumar, H.H.
Source : Defence Science Journal ; Vol:56(2) ; 2006 ; pp 269-278
Subject : 620.1 Material Science and Technology;669 Metallurgy
Keywords : Alumina;Silica;Magnesium oxide;Particle size;Surface area;Green density;Sintered density;Dielectric strength;Dielectric constant
Abstract : The paper presents the study of the particle size distribution, surface area and their effect on sintering of alumina (Al2O3) using additives such as magnesium oxide (MgO) and silica (SiO2), so that the samples could be sintered to high relative density (~ 97.43 %) with controlled grain growth. However, the use of MgO along with SiO2 on Al2O3 produced the powder compacts having high Green density, sintered density with minimum porosity to achieve high dielectric strength ceramic material, so that material can be used for high-voltage insulator applications. |
| | Polarographic Study of Cd Schiff Base Complex
Author : Patel, M.S.;Trivedi, T.;Vyas, D.N.
Source : Defence Science Journal ; Vol:29(1) ; 1979 ; pp 7-10
Subject : 621.315.592 Semiconductors
Keywords : Polarographic behaviour;DMF water media;Dielectric constant
Abstract : Polarographic behaviour of Cd/sup 2/+ with a schiff base salicyladehyde trisbuffer has been studied in DMF water media of three different compositions (viz., 0%, 30% and 50% v/v of DMF). Stability constant, free energy change delta G, enthalpy change delta H and entropy change delta S of the systems are calculated for all the three media at three different temperatures (viz., 30 degree centigrade, 40 degree centigrade and 50 degree centigrade). A relation of halfwave potential of the system with the dielectric constant of the medium has also been verified. |
| | Effect of Temperature on Aging of Ferroelectric Lead-Strontium- Zirconate-Titanate Ceramics
Author : Wathore, N.N.;Lonkar, C.M.;Kharat, D.K.
Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 683-686
Subject : 532.542 Fluid Dynamics;Defence Science Journal
Keywords : Computational fluid dynamics ;dielectric constant;ferroelectric ceramics;PSZT ceramics
Abstract : The effect of aging on Sr2+ modified lead-zirconate-titanate (PSZT) ceramics has been studied. Aging was assessed by the measurement of dielectric constant and dielectric loss tangent as a function of time and temperature. Dielectric constant and dielectric loss tangent were measured at different temperature ranges. Absolute rate of aging and relative rate of aging were determined. The PSZT ceramic showed sharp dielectric peak at 300 °C. The results shows that with increase temperature, both the dielectric constant and rate of aging increase. |
| | Novel Circuit for the Rapid Measurement of Dielectric Constant with Ultra Precision over a Wide Range of Frequencies
Author : Saxena, K.N. ;Wagh, V.W.
Source : Defence Science Journal ; Vol:30(4) ; 1980 ; pp 159-162
Subject : 621.38 Electronics
Keywords : Dielectric constant ;Electron ray tube
Abstract : A simplified instrument is designed for dielectric constant measurement of liquids and gases over a wide range of frequencies by using 6j5 as variable oscillator and 6E5 electron-ray tube for mechanical resonance indication with the quartz crystal of various frequencies. Measurements with the proposed new circuit are simple, rapid and accurate. |
| | Photo Dielectric Investigation of p Gallium Arsenide
Author : Farkya, V.K.;Bandopadhyaya, T.K.
Source : Defence Science Journal ; Vol:24(4) ; 1974 ; pp 145-146
Subject : 621.38 Electronics
Keywords : Photo excitation;Dielectric constant
Abstract : The complex dielectric constant of gallium arsenide sample was studied in the frequency range 0.3 to 30 MHz, subjected to photo-excitation. The model proposed by Dutt and Nicholls for after glow plasma seems to be in agreement with the experimental results. The relaxation time and damping have been estimated. |
| | Ferroelectric Properties and Transmission Response of PZN-PT Single Crystals for Underwater Communication
Author : Bubesh Babu, J.;Madeswaran, G.;Dhanasekaran, R.;Trinath, K.;Rao, A. V. N. R.;Prasad, N. S.;Abisekaraj, I. R.
Source : Defence Science Journal ; Vol:57(1) ; 2007 ; pp 89-93
Subject : 66 Chemical Technology
Keywords : Crystal growth;Sonar;Piezoelectric coefficient;Transducer;Underwater communication;PZN-PT single crystal;Electromechanical coupling factor;Dielectric constant;Ferroelectric constant
Abstract : Single crystal of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZN-PT) at the composition of morphotropic phase boundary (MPB) shows a very high electromechanical coupling coefficient, piezoelectric coefficient, and dielectric constant compared to conventional PZT ceramics. These exceptional properties of these single crystals find enormous applications in medical ultrasound imaging and underwater communication (Sonar). The growth of PZN-PT single crystals has been carried out by bottom-supported flux Bridgman method. There are many growth issues to be addressed during the process of growth. The grown crystals are oriented and cut along <001> direction with the crystal dimension of 8 x 6 x 1.5 mm3 for further analysis. The oriented crystals were poled at a rate of 1 kV/mm. The poled crystals have been characterised for dielectric, strain and piezoelectric values. Further, the poled specimen were tested for transmitting response at various frequencies in acoustic test facility and the difficulties in their growth. |
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