  Accurate and useful analytic approximations are developed for order parameter
profiles and interfacial tensions of phase-separated binary mixtures of
Bose-Einstein condensates. The pure condensates 1 and 2, each of which contains
a particular species of atoms, feature healing lengths $\xi_1$ and $\xi_2$. The
inter-atomic interactions are repulsive. In particular, the effective
inter-species repulsive interaction strength is $K$. A triple-parabola
approximation (TPA) is proposed, to represent closely the energy density
featured in Gross-Pitaevskii (GP) theory. This TPA allows us to define a model,
which is a handy alternative to the full GP theory, while still possessing a
simple analytic solution. The TPA offers a significant improvement over the
recently introduced double-parabola approximation (DPA). In particular, a more
accurate amplitude for the wall energy (of a single condensate) is derived and,
importantly, a more correct expression for the interfacial tension (of two
condensates) is obtained, which describes better its dependence on $K$ in the
strong segregation regime, while also the interface profiles undergo a
qualitative improvement.
