Elimination of pyrochlore phase in high‐concentration Sm³⁺‐doped PMN‐PT piezoelectric ceramics by excessive MgO

Abstract

Undesirable pyrochlore phase often appears in Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT)‐based ceramics with high rare‐earth ion (RE3+) doping concentration, which greatly limits their development. In this study, 0–5 mol% Sm3+‐doped Pb(Mg1/3Nb2/3)O3‐29PbTiO3 (PMN‐29PT:0‐5Sm) ceramics were first synthesized using traditional precursor method. In the X‐ray diffraction spectra and scanning electron microscope images of PMN‐29PT:3‐5Sm ceramics, the diffraction peaks of pyrochlore phase and pyrochlore grains with octahedral morphology were observed, respectively. The reason for the appearance of the pyrochlore phase is that Sm3+ doping causes the Nb‐rich regions. To eliminate the pyrochlore phase, PMN‐29PT:3‐5Sm ceramics were resynthesized by an improved precursor method in which an excess of 4 mol% MgO was added to the reactants before pre‐sintering. After adding an excess of 4 mol% MgO, the concentration ratio of Nb5+ and Mg2+ in the pyrochlore grains returned to the value in the perovskite grains, and the pyrochlore phase was transformed into the perovskite phase PMN. The dielectric, ferroelectric, and electromechanical properties were compared before and after eliminating the pyrochlore phase. The results show that the comprehensive performance of the ceramics is improved after eliminating the pyrochlore phase.

Miniature Ultrasound Transducer Incorporating Sm-PMN-PT 1-3 Composite

“…The temperature-dependent dielectric spectra of 2.5%Sm-0.72PMN-0.28PT ceramics at different frequencies are shown in Figure 5. It is obvious that the phenomena of dispersive phase transition (broadened dielectric and loss peaks) and frequency dispersion (dielectric and loss peaks move towards higher temperatures with increasing frequency) are the characteristics of relaxor ferroelectrics [28]. The Curie temperature T c of 2.5%Sm-0.72PMN-0.28PT ceramics was 81 • C, representing the temperature at which the phase transition occurs from a ferroelectric phase to a paraelectric phase at 1 kHz.…”

Sm and Mn doped enhancing the electrical properties of .68PMN–.32PT relaxor ferroelectric thin films

“…Li et al. have proved the Sm 3+ substitute Pb 2+ at the A site can reduce the oxygen vacancy concentration, thereby improving the dielectric and ferroelectric properties 11,12,15–19 . On the other hand, Mn‐doped can refine the grains, decrease the leakage current, and improve the remanent polarization 20–24 .…”

“…14 Li et al have proved the Sm 3+ substitute Pb 2+ at the A site can reduce the oxygen vacancy concentration, thereby improving the dielectric and ferroelectric properties. 11,12,[15][16][17][18][19] On the other hand, Mn-doped can refine the grains, decrease the leakage current, and improve the remanent polarization. [20][21][22][23][24] Therefore, appropriate addition of Sm 3+ and Mn 2+ can effectively inhibit the formation of oxygen vacancies in PMN-PT films, thereby reducing the leakage current and improving the quality of films.…”