  The Pockels effect is essential for controlling optical signals at the
highest speeds. We present the first measurements of the Pockels coefficients
and permittivity in lithium niobate (LN) and barium titanate (BTO) over a
continuous frequency range from 100 MHz to 330 GHz. These properties are
constant across this frequency range in LN but have a significant frequency
dependence in BTO. Still, our measurements show that BTO ($\varepsilon$ = 1136,
$r_{42}$ = 481 pm/V, $r_{33}$ = 125 pm/V at 100 MHz, $\varepsilon$ = 453,
$r_{42}$ = 191 pm/V, $r_{33}$ = 60 pm/V at 330 GHz) has remarkably large
electro-optic properties compared to LN ($\varepsilon$ = 27, $r_{42}$ = 15
pm/V, $r_{33}$ = 27 pm/V). Furthermore, we show how BTO devices can be designed
with a flat electro-optic frequency response despite the Pockels coefficient
dispersion. Finally, we expound our method for broadband characterization of
these vital electro-optic properties, utilizing specialized integrated
electro-optic phase shifters. Altogether, this work is foundational to
designing high-speed BTO devices and to developing new electro-optic materials.
