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Detailed Program
Paper Number : LP-I04
Time Frame : 17:20~17:45
Presentation Date : Thurseday, 27, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : Jae-Shin Lee
Session Chair 2# : Satoshi Wada
Synthesis of NaNbO3-BaTiO3 Lead-free Piezoelectric Ceramics using Submicron-sized Starting Materials
Rintaro Aoyagi
Nagoya Institute of Technology
PZT-based ceramics are widely used in piezoelectric devices such as actuator, ultrasonic generator, and resonator. Recently, it has been a strong demand to develop environmentally friendly lead-free piezoelectric materials. Many researchers have focused on alkaline niobate (ANbO3)-based piezoelectric materials as alternative candidates for lead-based substances. Among of them, sodium niobate NaNbO3 is a well-known anti-ferroelectric material and some NN-based perovskite solid solutions exhibit piezoelectric and ferroelectric properties above room temperature. It is considered that the control of domain size and grain size is one of key techniques for improvement of piezoelectric properties in lead-free material. Especially, the two-step sintering method using fine powder source is very effective to control the grain size for bulk ceramics. In this study, the (1-x)NaNbO3–xBaTiO3 (NNBTx) solid solution has been synthesized using submicron-sized BaTiO3 and NaNbO3 powders.
The submicron-sized NaNbO3 powder was synthesized by a molten salt method and average particle size of that was 180 nm. The NaNbO3 powder synthesized via molten salt method and commercially available BaTiO3 powder (100 nm: Sakai Chemical Ltd. BT-01) were mixed and the greens were prepared using mixture. The greens were sintered at 500–1220 ¡ÆC in order to investigate the reaction and grain growth.
In this study, BaTiO3 concentrations of x=0 and 0.1 were prepared. Sintering temperatures of both NNBT0 and NNBT0.1 ceramics prepared using molten salt NaNbO3 powder were 100 ¡ÆC lower than those prepared by mixed oxide and carbonate route. It was found that the starting materials of NaNbO3 and BaTiO3 reacts to a tetragonal NNBT-type perovskite structure at 1000 ¡ÆC and to start rapid grain growth and densification at >1100 ¡ÆC. The piezoelectric constant d33 and coupling factor kp of NNBT0.10 synthesized from fine powders were 145 pC/N and 0.34, respectively, which are larger than those of conventional samples.
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