SBIR-STTR Award

Active Signal Technologies, in collaboration with Novacap and Alfred University, will advance the development of two bismuth sodium titanate (NBT) ceramic materials with very promising dielectric properties across the temperature range -55°C to 300°C. The work will include enhanced formulation variants and improved processing techniques to optimize for permittivity, loss, breakdown voltage and resistivity. NBT-based materials were selected because Type H (the most mature example of the class) has low combined temperature and voltage coefficient resulting in a net capacitance change < 20% across the band from -40°C to +200°C at full voltage stress. At the end of Phase I the team will deliver 3 fully-packaged 1-ìF, 600-V multilayer capacitors of each type produced on standard manufacturing equipment in a production plant. The selected materials represent two different methods of achieving the same goal of very compact, reliable, temperature stable capacitors but with property mixes suitable for quite distinct power conditioning applications. Because ceramic capacitors raise concerns about adverse failure modes, the proposal addresses key issues of reliability with advanced sorting and quality control methods, and capacitor design for graceful degradation. In Phase II nano processing is introduced to reduce intrinsic flaw size and raise breakdown strength.

Keywords:
Capacitors, Electroceramic, High Temperature, Dielectric, Power Electronics, Bismuth Sodium Titanate, Bnt, Ferroelectrics.

Phase II of the present program will produce capacitors and modules that meet the Air Force need for ultra-stable electrical properties (loss < 0.1%, permittivity ~2,000 <+/- 5% from -55 – 300°C) with high insulation resistance (>> 1-OhmF at 250°C), and graceful performance degradation. Initial optimization work by the team of Active Signal Technologies, Alfred University, Novacap and Lockheed Martin will enable a down-selection between two dielectric formulations and two alternative processing routes based on full characterization and testing of MLCs and 6 - 10-uF modules prepared from the candidate systems scaled up and fabricated in a manufacturing plant. One material system uses niobium substitution of the baseline NBT dielectric while the other integrates the outstanding properties of a high-temperature-stable (NBT-ST) and a low-temperature-stable (PMN-ST) dielectric material. Module development will proceed from a compact low inductance prototype developed in Phase I through iterations of fuse development at the 6 and 10-uF scale to demonstrate individual drop-out of failing capacitors under extreme testing conditions without energetic or propagating damage to the remainder of the module. The down-selected dielectric system will be further refined and used to prepare a large batch of ~1-uF capacitors for manufacture of the final deliverable 20-uF fused module.

Keywords:
Capacitors, High Current, High Frequency, Pmn, Nbt, Low Temperature, High Temperature