The characteristics of the diffuse phase transition in Mn doped Pb(Fe2/3W1/3)O-3 relaxor ceramics

The characteristics of the diffuse phase transition of Pb(Fe2/3W1/3)O-3 rel axor ceramics doped with different amounts of Mn are investigated. The free zing temperature T-f, obtained by fitting the omega, T-max to the Vogel-Ful cher relationship, clearly changes with the Mn content. It increases as the Mn content increases, approaching the T-max(1 MHz) value of the relaxor cu rve. A concomitant decrease in the frequency dispersion of T-max is also ob served. The freezing temperature also increases as the 1: 1 order of Fe3+ a nd W6+ on B sites increases by air annealing but decreases by oxygen anneal ing. It is suggested that the Mn ions, which are predominantly compensated by oxygen vacancies, form with them defect pairs and that these pairs can c ouple to the spontaneous polarization vectors, increasing the correlation b etween the dipole moments and originating the increase of the freezing temp erature. It is further suggested that filling up the oxygen vacancies by ox ygen annealing will decrease the defect pairs and cause the opposite effect . (C) 1999 American Institute of Physics. [S0021-8979(99)02304-X].