Browsing by Author "Liu, Yuan-Wen"

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Effects of P2+ doping on La4Ti9O24 ceramics
(2006-08-01)
Liu, Yuan-Wen
;
Lin, Pang
;
Chu, Ming-Wen
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The kinetic structural evolution of the Pb2+-doped La4Ti9O24 ceramics was investigated. Using electron diffraction and Rietveld analysis of the X-ray powder diffraction patterns, we show that the increase in Pb2+ doping results in the structural transition from La4Ti9O24 to a La2/3TiO3-type phase (Ibmm, No. 74). Further kinetic studies of Pb2+ diffusion into La4Ti9O24 ceramics suggest that the La4Ti9O24-La2/3TiO3 phase transition requires an activation energy of 607 +/- 60 kJ/ mol..
Phase formation and microwave dielectric properties of Pb2+ and Sr2+ doped La4Ti9O24 ceramics
(2006-10-12)
Liu, Yuan-Wen
;
Lin, Pang
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Phase formation and microwave dielectric properties of the Pb2+ and Sr2+ doped La4Ti9O24 ceramics were investigated. Using electron diffraction and Rietveld analysis of the X-ray powder diffraction patterns, we show that the increase in the concentration of Pb2+ and Sr2+ doping results in the structural transition from La4Ti9O24 to a La2/3TiO3-type phase (Ibmm, No. 74). A change in the crystalline phase considerably affects the microwave dielectric properties, increasing the epsilon(r) from 37 to 130, reducing Q x f from 25.000 to 5500, and increasing temperature coefficient of the resonant frequency (TCF) from 15 to 300 ppm/degrees C. (C) 2006 Elsevier Ltd. All rights reserved.