In consideration of the numerous electrogravitic effects that have been documented, it is clear that gravity is an electrical phenomenon.
In the 1990s, Morton Spears published two books outlining his capacitance theory of gravity.
Start with two plates of a vacuum-spaced capacitor connected to a DC voltage supply (battery). The two plates will mutually attract each other.
If the capacitance theory of gravity is correct, the force of gravity hinges on the positive dielectric constant of all known materials. I would predict that piezoelectric materials resonated at their resonant frequency have a negative dielectric constant, hence their antigravity effect.