Barium titanate-added lead nickel niobate ferroelectrics: Accelerated perovskite formation and dielectric properties
- PDF / 218,227 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 18 Downloads / 215 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Barium titanate-added lead nickel niobate ferroelectrics: Accelerated perovskite formation and dielectric properties Chung-Hsin Lua) and Jai-Fang Wu Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China (Received 21 February 1996; accepted 16 May 1996)
The addition of BaTiO3 to Pb(Ni1/3 Nb2/3 )O3 has been confirmed to vary the formation kinetics of the perovskite solid solutions of Pb(Ni1/3 Nb2/3 )O3 –BaTiO3 , and to suppress the generation of the pyrochlore phase. A semiquantitatively calculated reaction conversion verified that increasing the BaTiO3 content significantly accelerated the formation of the perovskite solid solutions. The formed solid solutions of Pb(Ni1/3 Nb2/3 )O3 –BaTiO3 (up to 90 mol % of BaTiO3 ) exhibited a cubic symmetry at room temperature. The lattice parameter monotonously decreased with an increase in the BaTiO3 content. The structural stability of the perovskite phase was found to be enhanced by the addition of BaTiO3 as well. The formed solid solutions were able to maintain the perovskite structure without decomposition when heated up to 1250 ±C. The frequency dependence of the apparent Curie temperature and the diffuseness of the dielectric peak of sintered specimens were increased with increasing the BaTiO3 content up to 50 mol %. Whereas with further addition, the relaxor characteristics in the specimens became obscure, associated with lower frequency dependence and less broadening of the dielectric maximum. The largest broadening of the dielectric peak occurred at x 0.5, implying that this composition exhibited the most disordered structure, which is probably related to the most random arrangement of B-site cations in oxygen octahedran.
I. INTRODUCTION
Lead nickel niobate (Pb(Ni1/3 Nb2/3 )O3 )-containing ceramics are important materials for dielectric and piezoelectric devices. Pb(Ni1/3 Nb2/3 )O3 itself exhibits disordered perovskite structure and typical relaxor ferroelectric properties.1,2 Adding other relaxor materials to Pb(Ni1/3 Nb2/3 )O3 can form perovskite solid solutions. These solid solutions possess high dielectric permittivity and low sintering temperature, and can be utilized in the low-temperature sintering multilayer ceramic capacitors.3,4 On the other hand, the Pb(Ni1/3 Nb2/3 )O3 –Pb(Zr, Ti)O3 system exhibits both excellent piezoelectricity and sintering properties, and becomes a promising candidate for the use in actuators.5,6 In spite of the potential application of the Pb(Ni1/3 Nb2/3 )O3 -based materials in electronic devices, one major problem is the difficulty in the synthesis of pure perovskite compounds. The pyrochlore phase tends to coexist with the perovskite phase. The presence of the pyrochlore phase has negative effects on both the dielectric and piezoelectric properties of ceramics.7 For improving the electric properties, it is crucial to eliminate the pyrochlore phase. Columbite precursors are generally used to prepare relaxor-containing ceramics. In most relaxor
Data Loading...
