NEUTRON DERACTION INVESTIGATION OF THE FRL-FRH TRANSITION IN Nb DOPED PbZr1-x TIxO3 WITH x=0.035

Neutron powder diffraction data have been collected in order to characterize the F(RL)-F(RH) transition of Nb-doped, Zr-rich PZT. Data for the first few ditbction peaks were obtained in the temperature range 27 <= T <= 350 K in order to make a detailed characterization of the F(RL)-F(RH) transition, which takes place for this composition at T(LT)congruent to 323 K. The temperature dependence of the Pb and Zr/Ti(Nb) atomic shifts, and the rotation and distortion of the oxygen octahedra through the transition was derived. The results are compared with published data for PZT with x=0.10, and indicate that (a) the change in Zr/Ti(Nb) shift through T(LH) becomes more pronounced, and (b) the & ortion and tilt of the oxygen octahedra below T(LH) become more important for x=0.035 than for x=0.10. It has been conduded that the increment in the variation of the spontaneous polarization through T(LH) with increasing Zr amount is matnly caused by the increase of the Zr/Ti(Nb) displacement in the low temperature rhombohedral phase.