Perovskite crystallization kinetics and dielectric properties of the PMN-PT films prepared by polymer-modified sol-gel p
- PDF / 1,430,186 Bytes
- 9 Pages / 584.957 x 782.986 pts Page_size
- 4 Downloads / 176 Views
T.S. Zhang Institute of Materials Research and Engineering, Research Link, Singapore 117602
M.M. Zhu School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798
J. Maa) Temasek Laboratories, Nanyang Technological University, Singapore 639798; and School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Received 17 September 2008; accepted 12 January 2009)
Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT, 43% PT) thin films have been developed by modified sol-gel processing with polyvinylpyrrolidone (PVP) as a modifier and lead nitrate as a lead source. With PVP modification, perovskite phase was directly crystallized from amorphous film matrix at a temperature as low as 430 C, and the crystallinity was significantly enhanced. Kinetics studies show that the crystallization process is controlled by heat transfer phenomena at the annealing temperatures 460 C. At higher annealing temperatures (550–700 C), it is a diffusion-controlled reaction with an activation energy of 167.7 kJ/mol, almost two times lower than that for the films without PVP modification. The promotion mechanism of perovskite crystallization by PVP addition has been discussed accordingly. The resultant films consisted of nanocrystallines and exhibited relaxor-like dielectric behavior, although the composition of the films located in normal ferroelectrics. I. INTRODUCTION 1
Initiated by Pechini in the 1960s, polymer species played an increasingly important role in the sol-gel processing of various oxide films, especially at the beginning of this century. The polymers with carbonyl and/or ether groups can form complexes with metal ions and sterically entrap them in an entangled polymer network, resulting in homogenous and stable solutions. Furthermore, the combustion of polymers generates a large amount of heat and increases the in situ temperature of the gel particles. As a result, intermediate phases can be suppressed and single-phase materials can be obtained. For example, polyethylenimine (PEI) has been used in the synthesis of pure oxide films like SrTiO3, Ba1-xSrxTiO3, and TiO2.2 Polyethylene glycol (PEG), polyvinyl alcohol (PVA), and poly(vinyl acetate) (PVAc) have been used to prepare single-phase oxides such as calcium aluminate (CaAl2O4), yttrium aluminate (Y3Al5O12), yttrium phosphate(YPO4), and Pb(Zr,Ti)O3 (PZT).3–5 PEG was also applied to deposit Pb(Zn1/3Nb2/3)O3 (PZN)-based ferroelectric thin films.6 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0181
1576
http://journals.cambridge.org
J. Mater. Res., Vol. 24, No. 4, Apr 2009 Downloaded: 13 Mar 2015
In addition, polymers can increase the viscosity of the sol-gel solutions and relax the thermal stress produced during crystallization of gel films by forming chemical bonds with the gel network. As a result, crack-free films with a high critical thickness (maximum one-coating thickness without cracking) can be obtained. Polyvinylpyrrolidone (PVP), as a stress-relaxing agent
Data Loading...
