Journal of Student Research 2014

Barium Titanate & Barium Titanate/Aluminum Oxide Ceramics...

Barium Titanate and Barium Titanate/Aluminum Oxide Ceramics for Capacitors and Transducers Lewis E. Brigman and Jake Pedretti | Seniors B.S. in Manufacturing Engineering Abstract An inexpensive solid-state powder compaction and sintering method to make barium titanate disc structures for use in capacitors and piezoelectric transducers was researched. Barium titanate powders were uniaxially pressed to 20,000 lbf into discs and sintered over 1,100 to 1,400°C for different times. The discs were characterized for density, capacitance, and output voltage characteristics under uniaxial compression. The output voltage exhibited an exponential relationship with disc thickness. The experimental relative permittivity revealed a trend with percent porosity similar to the theoretical predictions. To strengthen BaTiO 3 against cracking during mechanical and electrical loading, BaTiO 3 /xA l2 O 3 (x = 0, 5, 10 and 15 percent by weight) composites were prepared by ball-milling, compaction, and sintering (1,250°C and 1,350°C, 1h and 4h). The density and flexural strength of sintered composites decreased and porosity content increased as the amount of Al 2 O 3 increased. Because of high incidence of porosity, the composite samples did not develop their full strengthening potential. Recommendations have been made to further expand this research and achieve higher strength in BaTiO 3 /xAl 2 O 3 composites. Keywords : powder metallurgy, piezoelectric ceramics, composites, capacitance, flexural strength, densification Introduction Barium titanate (BaTiO 3 ) is a ferroelectric ceramic with piezoelectric properties. It is used in multilayer capacitors in TVs, video cameras and computers. It is also used as a piezoelectric transducer in microphones and in power generation devices. The

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