  Under application of an electric field greater than a triggering electric
field $E_c \sim 0.4$ kV/mm, suspensions obtained by dispersing particles of the
synthetic clay fluoro-hectorite in a silicon oil, aggregate into chain- and/or
column-like structures parallel to the applied electric field. This
micro-structuring results in a transition in the suspensions' rheological
behavior, from a Newtonian-like behavior to a shear-thinning rheology with a
significant yield stress. This behavior is studied as a function of particle
volume fraction and strength of the applied electric field, $E$. The steady
shear flow curves are observed to scale onto a master curve with respect to
$E$, in a manner similar to what was recently found for suspensions of laponite
clay [42]. In the case of Na-fluorohectorite, the corresponding dynamic yield
stress is demonstrated to scale with respect to $E$ as a power law with an
exponent $\alpha \sim 1.93$, while the static yield stress inferred from
constant shear stress tests exhibits a similar behavior with $\alpha \sim
1.58$. The suspensions are also studied in the framework of thixotropic fluids:
the bifurcation in the rheology behavior when letting the system flow and
evolve under a constant applied shear stress is characterized, and a
bifurcation yield stress, estimated as the applied shear stress at which
viscosity bifurcation occurs, is measured to scale as $E^\alpha$ with $\alpha
\sim 0.5$ to 0.6. All measured yield stresses increase with the particle
fraction $\Phi$ of the suspension. For the static yield stress, a scaling law
$\Phi^\beta$, with $\beta = 0.54$, is found. The results are found to be
reasonably consistent with each other. Their similarities with-, and
discrepancies to- results obtained on laponite-oil suspensions are discussed.
