Ferroelectrics for microwave applications

Hello

I want to know:

1. In Ferroelectrics how do the the dielectric properties analytically vary with respect to DC bias voltage? Can we model this, and can we use such models in the design of Microwave circuits using EM Simulation tools like Ansoft Designer/HFSS?

2. How can we analytically model the response time for the dielectric constant change in the ferroelectric material?

Thanks
Poonam