Polarization switching behavior and energy storage performances of (Pb 1x La x )(Zr 0.90 Ti 0.10 ) 1x/4 O 3 (PLZT x/90/10) ceramics with La compositions across the ferroelectric/antiferroelectric phase boundary, which show variable amount of antiferroelectric (AFE) orthorhombic and ferroelectric (FE) rhombohedral phases, were investigated. A low AFE to FE switching field was obtained and its value could be adjusted by La chemical modification. While the PLZT system evolves from a FE state to an AFE state as a function of La content and from an AFE state to a FE state as a function of the applied electric field, the recoverable energy (W re ) and loss energy (W loss ) range between two limits whose lower and higher values are obtained for PLZT composition in AFE state and FE state, respectively. In terms of the extent of La-modification, the W re has been enhanced from 0.819 J/cm 3 (for PLZT 2/90/10 and electric field of~30 kV/cm) to the highest value of 1.85 J/cm 3 (for PLZT 3.5/90/10 and electric field 65 kV/cm), followed by their subsequent reduction.Eight (Pb 1Àx La x )(Zr 0.90 Ti 0.10 ) 1Àx/4 O 3 (PLZT x/90/10) ceramic compositions across the FE/AFE phase boundary were selected (with La 3+ content x = 0.020, 0.030, 0.031, 0.032, G. L. Brennecka-contributing editor Manuscript No. 37930.

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We present the results of dielectric and anelastic spectroscopy measurements, together with X-ray diffraction investigations, which allow us to establish more precisely the phase diagram of Pb1−xLax(Zr0.9Ti0.1)1−x/4O3 (PLZT x/90/10) in the compositional range around the AFE/FE phase boundary (0 < x < 0.04). From structural analysis and polarization-electric field measurements, we have found that the ground state of PLZT samples with x < 0.025 is rhombohedral R3c, while samples with x > 0.032 are antiferroelectric with orthorhombic Pbam structure. In-between, for compositions with 0.025 ≤ x ≤ 0.032, a coexistence of the AFE/FE phases is evidenced. The use of complementary dielectric and anelastic techniques allows to follow the phase transitions shifts throughout all the interesting composition range and to construct the temperature-composition phase diagram. The tilt instability line, separating the R3c and R3m low and high temperature phases, has been evidenced. Moreover, the new transition, associated with the onset of disordered tilting preceding the long range order of the R3c phase, previously found in Zr-rich Pb(Zr,Ti)O3, is confirmed in rhombohedral PLZT x/90/10 compositions.