| || 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.
| || InP Based Devices
Author : Bose, D.N.
Source : Defence Science Journal ; Vol:39(4) ; 1989 ; pp 425-434
Subject : 621.38 Electronics;548 Crystallography;548.2 Crystal Growth
Keywords : Optoelectronic devices;Crystal growth
Abstract : The frontiers of solid-state devices and integrated circuits are moving towards higher frequencies, output powers and efficiencies. There is also increasing emphasis on the development of optoelectronic devices. In this endeavour InP-based devices are playing a major role. These devices include TEDs, IMPATTS, MISFETs on the one hand and LED, lasers, solar cells and photodetectors on the other. The latest on the scene are devices based on heterostructurs and two-dimensional transport such as HBTs and HEMTs. This review highlights salient differences between InP and GaAs commencing with crystal growth, defect and surface properties and discusses some recent results on MISFETS, radiation-resistant solar cells, HEMTs and HBTs. The relation between physical properties and device performance as applicable to InP and GaAs are clearly brought out.