The dielectric properties of the terpolymer were also measured after being subjected to an electric field of 100 MV/m at 50◦C for 10 min, similar to the poling conditions applied to the copolymer. There is essentially no change in the dielectric βr process before and after the application of the electric field, which is expected for the ferroelectric relaxor poled at temperatures where the slim polarization loop is observed. This supports complete conversion to the ferroelectric relaxor phase in this terpolymer.