Peculiar dynamics of polar states at the morphotropic phase boundary of antiferroelectric Pb(Zr1-xTix)O3

The coexistence of several structural instabilities in Zr-rich Pb(Zr,Ti)O3 leads to the possibility of condensing them successively to trigger a sequence of phase transitions, instead of reaching directly the AFE phase, as in pure PbZrO3. This is especially noticeable in compositions near the antiferroelectric morphotropic phase boundary and the tricritical point around room temperature, as PZT 95/5, where three phases are energetically available. To check the thermal development of these different phases, differential scanning calorimetry, dielectric spectroscopy and Raman scattering experiments were carried on antiferroelectric morphotropic-adjacent ceramics PZT 96/4 and 95/5. They revealed a complicated and hysteretic thermal behaviour due to the complex microstructure and the coexistence of regions with different phases within the samples. On heating and cooling the ceramics show two intermediate polar phases between the cubic paraelectric and the low temperature antiferroelectric phase, which are attained under different experimental conditions and specific pre-history. Our results suggest that ceramics with composition near PZT 95/5 are potential materials for novel room temperature device applications. An innovative approach of phase-control is proposed, based on the thermal behaviour of the intermediate polar states observed and using small temperature gradients by appropriate heating-cooling cycles.