Stabilization of lead lithium iron tungstate with adding barium titanate
- PDF / 203,000 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 61 Downloads / 164 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Stabilization of lead lithium iron tungstate with adding barium titanate Chung-Hsin Lu and Buh-Kuan Fang Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China (Received 5 May 1995; accepted 5 August 1996)
The kinetics of formation, phase stabilities, and dielectric constants of Pb(Li1/4 Fe1/4 W1/2 )O3 and BaTiO3 -added Pb(Li1/4 Fe1/4 W1/2 )O3 have been compared. The addition of 2 mol % BaTiO3 in Pb(Li1/4 Fe1/4 W1/2 )O3 was confirmed to promote the complete formation of the perovskite phase at 700 ±C. Also, the thermal stability of the perovskite phase was significantly enhanced, which resulted in an increase of the dielectric permittivity.
Low-temperature sintering is a crucial technology for fabricating multilayer ceramic capacitors in which AgyPd alloy is utilized as inner electrodes. For reducing the sintering temperatures of dielectric ceramics, various kinds of flux materials such as PbO or Bi2 O3yLi2 O have been used as sintering aids in BaTiO3 or relaxorbased systems.1,2 One of the potential sintering aids is lead lithium iron tungstate Pb(Li1/4 Fe1/4 W1/2 )O3 . This material possesses relaxor-ferroelectric characteristics, and exhibits perovskite structure with a partially ordered arrangement of cations in octahedral sites.3,4 Because of the dielectric properties and low partial-melting temperature, Pb(Li1/4 Fe1/4 W1/2 )O3 has been used to enhance the sintering of relaxor systems such as Pb(Mg1/3 Nb2/3 )O3 and Pb(Fe2/3 W1/3 )O3 –Pb(Fe1/2 Nb1/2 )O3 .5,6 In spite of the usefulness of Pb(Li1/4 Fe1/4 W1/2 )O3 in the low-temperature sintering process, the pure perovskite phase of Pb(Li1/4 Fe1/4 W1/2 )O3 is rather difficult to synthesize.7 The difficulties in obtaining pure Pb(Li1/4 Fe1/4 W1/2 )O3 compound are twofold. The first is that the reaction process of Pb(Li1/4 Fe1/4 W1/2 )O3 has to pass through the formation of lead tungstates (PbWO4 and Pb2 WO5 ). The lead tungstates will remain as intermediates in specimens when reactions cannot completely progress due to insufficient reaction time/temperature or poor mixing of reactants. The second lies in the thermodynamic instability of Pb(Li1/4 Fe1/4 W1/2 )O3 at elevated temperatures. This compound tends to partially decompose at above 720 ±C, causing the formation of Pb2 WO5 . Since the synthesis temperature (710 ±C) is very close to the decomposition temperature, improper heating conditions will result in the partial decomposition of Pb(Li1/4 Fe1/4 W1/2 )O3 . Addition of stable perovskite compounds such as BaTiO3 , SrTiO3 , or PbTiO3 has been reported to effectively suppress the formation of pyrochlore phase in lead-based relaxor compounds.8–11 In this study, in order to obtain the pure perovskite phase of Pb(Li1/4 Fe1/4 W1/2 )O3 , BaTiO3 was utilized as an additive. The effects J. Mater. Res., Vol. 12, No. 1, Jan 1997
http://journals.cambridge.org
Downloaded: 30 Mar 2015
of addition of BaTiO3 on the decomposition behavior of Pb(Li1/4 Fe1/4 W1/2 )O3 at elevated temperatu
Data Loading...
