  The current controversies about the existence of an intermediate 'beta' phase
of BiFeO_3 and the high temperature paraelectric 'gamma' phase are resolved by
studying the sequence of ferroic transitions in
0.8BiFeO_3-0.2Pb(Fe_1/2Nb_1/2)O_3 (BF-0.2PFN) with lowered transition
temperature. It is shown that the room temperature ferroelectric phase of
0.8BF-0.2PFN in the R3c space group transforms to the paraelectric/paraelastic
cubic (Pm-3m) phase directly without any intermediate 'beta' phase reported in
the literature. This transition is of first order type as confirmed by the
coexistence of R3c and Pm-3m phases over a 100K range and a discontinuous
change in the unit cell volume.
