Effects of glass elements on the structural evolution of in situ grown ferroelectric perovskite crystals in sol-gel deri
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Effects of glass elements on the structural evolution of in situ grown ferroelectric perovskite crystals in sol-gel derived glass-ceramics Kui Yao and Weiguang Zhu Microelectronics Center, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798
Liangying Zhang and Xi Yao Electronic Materials Research Laboratory, Xi’an Jiaotong University, Xi’an 710049, China (Received 25 April 1996; accepted 28 October 1996)
Several ABO3 perovskite ferroelectric crystals, PbTiO3 , Pb(Zr, Ti)O3 , and BaTiO3 have been in situ grown from amorphous gels with glass elements, and the structural evolution has been systematically investigated using x-ray diffraction (XRD), infrared spectra (IR), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and dielectric measurements. It is found that in the Si-contained glass-ceramic systems, Si and B glass elements are incorporated into the crystalline structures, resulting in the variation of the crystallization process, change of lattice constant, and dielectric properties. Some metastable phases expressed by a general formula Ax By Gz Ow (A Pb and Ba; B Zr and Ti; G for glass elements, especially for Si) have been observed and discussed.
I. INTRODUCTION
Ferroelectric PbTiO3 and BaTiO3 based glassceramics have stimulated interesting research activity and showed great potential in certain important electronic applications since the 1960s.1–4 The advantages of ferroelectric glass-ceramics such as lower sintering temperature and more homogeneous mixing of ferroelectric phases with glass have been utilized as thick film capacitor pastes and electronic sealing materials.5–7 In recent years, such glass-ceramics have also been used in ferroelectric, piezoelectric, and pyroelectric applications.8–12 Conventional glass-ceramics have been fabricated using the melting-quenching technique.1–12 This technique not only needs heavy capital cost for equipment, but also has difficulty in preparing the multiple-component glass-ceramics due to the very high melting temperature and high volatility of some elements at elevated temperatures. In recent years, the sol-gel technique has become an emerging technology to prepare various samples, especially for multiple-component systems. Compared to the melting-quenching technique, this chemical approach for preparing glass-ceramics has several of the following obvious advantages: (i) not going through a melting stage at elevated temperatures; (ii) no need for costly equipment for the rapid quenching; (iii) easy control of compositions, especially for systems containing volatile elements like Pb, B, and Hg; and (iv) ability to make thin films with uniform compositions over large areas. Recently, the sol-gel process has J. Mater. Res., Vol. 12, No. 4, Apr 1997
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also been employed as a novel technique for preparing ferroelectric glass-ceramics.13–16 It is well known that microstructures and physical prope
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