Formulations for voltage switchable dielectric material having a stepped voltage response and methods for making the same
Formulations for voltage switchable dielectric materials include two or more different types of semiconductive materials uniformly dispersed within a dielectric matrix material. The semiconductive materials are selected to have different bandgap energies in order to provide the voltage switchable dielectric material with a stepped voltage response. The semiconductive materials can comprise inorganic particles, organic particles, or an organic material that is soluble in, or miscible with, the dielectric matrix material. Formulations optionally can also include electrically conductive materials. At least one of the conductive or semiconductive materials in a formulation can comprise particles characterized by an aspect ratio of at least 3 or greater.
1. A voltage switchable dielectric material comprising:
a dielectric matrix material;
a first semiconductive material characterized by a first bandgap energy and disposed within the matrix material;
a second semiconductive material disposed within the dielectric matrix material and characterized by a second bandgap energy different than the first bandgap energy; and
a third semiconductive material disposed within the dielectric matrix material and characterized by a third bandgap energy different than the first and second bandgap energies.
2. The voltage switchable dielectric material of claim 1 wherein the first semiconductive material disposed within the dielectric matrix material comprises particles.
3. The voltage switchable dielectric material of claim 1 further comprising an electrically conductive material disposed within the matrix material.
4. The voltage switchable dielectric material of claim 1 wherein the dielectric matrix material is selected from a group consisting of silicone polymer, phenolic resin, epoxy, polyurethane, poly(meth) acrylate, polyamide, polyester, polycarbonate, polyacrylamides, polyimide, polyethylene, polypropylene, polyphenylene oxide, polysulphone, ceramer, polyphenylene sulfone, siloxane, and polyphosphazine.
5. The voltage switchable dielectric material of claim 1 wherein the second bandgap energy is in the range of about 2 eV to 3 eV.
6. The voltage switchable dielectric material of claim 5 wherein the first bandgap energy is less than 2 eV and the third bandgap energy is greater than 3 eV.
7. A voltage switchable dielectric material comprising:
a dielectric matrix material;
particles of a first semiconductive material characterized by a first bandgap energy and disposed within the matrix material, the particles of the first semiconductive material further characterized by an aspect ratio of at least 3:1; and
a second semiconductive material disposed within the dielectric matrix material and characterized by a second bandgap energy different than the first bandgap energy.
8. The voltage switchable dielectric material of claim 7 further comprising an electrically conductive material disposed within the matrix material.
9. The voltage switchable dielectric material of claim 7 wherein the particles of the first semiconductive material include particles of a material selected from the group consisting of single walled nanotubes, multiwalled nanotubes, fullerenes, semiconductive nanorods, and semiconductive nanowires.
10. The voltage switchable dielectric material of claim 7 wherein the second semiconductive material include particles of a material selected from the group consisting of silicon, silicon carbide, boron nitride, aluminum nitride, nickel oxide, zinc sulfide, bismuth oxide, iron oxide, tungsten oxide, and titanium dioxide.
11. The voltage switchable dielectric material of claim 7 wherein the aspect ratio of the particles of the first semiconductive material is at least 1000:1.
12. A voltage switchable dielectric material comprising:
a dielectric matrix material;
particles of an electrically conductive material disposed within the matrix material and characterized by an aspect ratio of at least 3:1;
a first semiconductive material characterized by a first bandgap energy and disposed within the matrix material; and
a second semiconductive material disposed within the dielectric matrix material and characterized by a second bandgap energy different than the first bandgap energy.
13. The voltage switchable dielectric material of claim 12 wherein the particles of the electrically conductive material are selected from the group consisting of electrically conductive nanorods, nanowires, single walled nanotubes, multiwalled nanotubes, and fullerenes.
14. The voltage switchable dielectric material of claim 12 wherein the first semiconductive material includes particles of a material selected from the group consisting of silicon, silicon carbide, boron nitride, aluminum nitride, nickel oxide, zinc sulfide, bismuth oxide, iron oxide, and titanium dioxide.
15. The voltage switchable dielectric material of claim 12 wherein the first semiconductive material comprises particles also characterized by an aspect ratio of at least 3:1.
16. The voltage switchable dielectric material of claim 12 wherein a volume percentage of conductive particles is less than about 35.