  We investigate the relaxation and conduction mechanism of Ba0.90Sr0.10TiO3
(BST) ceramic, synthesized by the solid state reaction method. The dielectric
and relaxation properties are analyzed in the temperature range of
380-450{\deg}C with alternative current in the frequency range of 20Hz-1MHz.
Variation of dielectric constant, \epsilon', with temperature shows a normal
ferroelectric transition at Tc=95{\deg}C with a weak degree of diffuseness. The
modified Cole-Cole equation is used to describe all contributions to the
relaxation mechanism. The frequency exponent m({\omega},T) deduced from
experimental data of the dielectric loss ({\epsilon}") as m({\omega},
T)=($\partial$ ln {\epsilon}"/$\partial$ ln {\omega}) shows a temperature and
frequency dependence. Two conduction process are observed: non-overlapping
small-polaron tunneling (NSPT) at low frequencies and overlapping large polaron
tunneling (OLPT) at high frequencies. The analysis of Nyquist plots reveals
also the presence of two contributions, who which the activation energies have
been calculated.
