Effects of intermediate deformation and thermal processing in the OPIT process upon critical current density of Ag/BiSSCO tapes
Critical current density, J/sub c/, of Ag/Bi(Pb)SCCO tapes in as-deformed and as-sintered states were studied at different stages of tape processing. Intermediate pressing and rolling result in significant I/sub c/ degradation. Non-zero I/sub c/ remains after the applications of pressing load up to 11 and 8 GPa following the third and first sintering, respectively. Under rolling conditions I/sub c/ remains non-zero up to maximum tape thickness reduction of 20%. Bending tests show that I/sub c/ reduction is the result of deformation-induced micro-crack formation which are easily healed during the first hour of the next sintering. Intermediate deformation after the first sintering cycle has been shown to accelerate significantly the 2212 to 2223 phase transformation during the first hours of the second sintering step. I/sub c/ growth during the first hour of the second sintering cycle is not connected with that phase transformation and is presumed to be the result of pinning ability and structure connectivity enhancement.
TOPICAL REVIEW: The mechanical deformation of superconducting BiSrCaCuO/Ag composites
The mechanical deformation of BiSrCaCuO/Ag composites made by the powder-in-tube method is a multi-step process. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. A key parameter is the core density, which changes during mechanical deformation. In this review, basic concepts of the classical mechanical deformation theory are briefly discussed. Simple descriptions of deformation processes like pressing, rolling, drawing and extrusion are also presented. The term `freedom parameter', , is introduced to illustrate the influence of various constraint factors on the mass-flow behaviour. Simple pictures including mass redistribution and the powder-flow model are presented for interpreting the plastic deformation process of the composites. Experimental results are reviewed and our proposed pictures and models are applied for discussion.
Third order nonlinear distortion of SAW duplexers in UMTS system
Nonlinearity distortion characterization and accurate modeling techniques for leaky surface acoustic wave (LSAW) devices have been desired in the recently years due to the applications of the Radio Frequency (RF) SAW duplexers in the third-generation (3G) telecommunication system, such as Universal Mobile Telecommunications System (UMTS). In the work, we first discuss the approaches to measure and characterize the 3rd order harmonic generation of the resonators on lithium tantalate YXl42° wafer and YXl48° wafer, with resonance frequency of 800MHz to 900 MHz; Second, we present an effective nonlinear Butterworth-van-Dyke (BVD) model to simulate the multi-tone 3rd order intermodulation effects of a band 5 duplexer; simulation result vs. measurement of 3rd order harmonic generation, 3rd order intermodulation (IMD3) and triple beat are presented.