  We study the scaled-energy (x_B) distribution of bottom-flavored hadrons (B)
inclusively produced in top-quark decays at next-to-leading order (NLO) in the
general-mass variable-flavor-number scheme endowed with realistic,
nonperturbative fragmentation functions that are obtained through a global fit
to e^+e^- data from CERN LEP1 and SLAC SLC exploiting their universality and
scaling violations. Specifically, we study the effects of gluon fragmentation
and finite bottom-quark and B-hadron masses. We find the NLO corrections to be
significant. Gluon fragmentation leads to an appreciable reduction in the
partial decay width at low values of x_B. Hadron masses are responsible for the
low-x_B threshold, while the bottom-quark mass is of minor importance.
Neglecting the latter, we also study the doubly differential distribution
d^2Gamma/[dx_B dcos(theta)] of the partial width of the decay t -> b W^+ -> B
l^+ nu_l + X, where theta is the decay angle of the charged lepton in the
W-boson rest frame.
