Tuning Nb Solubility, Electrical Properties, and Imprint through PbO Stoichiometry in PZT Films

Area of Science:

• Materials Science
• Solid State Chemistry
• Thin Film Technology

Background:

• Lead zirconate titanate (PZT) is a key material for piezoelectric applications.
• Controlling stoichiometry and phase purity is essential for optimizing PZT properties.
• Niobium (Nb) doping is explored to modify PZT characteristics.

Purpose of the Study:

• To investigate the effect of high Nb concentrations on PZT film stoichiometry and phase.
• To determine optimal PbO excess levels for achieving phase-pure perovskite Nb-doped PZT films.
• To analyze the impact of Nb doping and stoichiometry control on dielectric and piezoelectric properties.

Main Methods:

• Chemical solution deposition of Nb-doped PZT films with varying Nb (6-13 mol%) and PbO excess concentrations.
• X-ray diffraction (XRD) for phase analysis.
• Dielectric and piezoelectric property measurements (permittivity, remanent piezoelectric coefficient).
• Analysis of internal bias field and imprint characteristics after thermal poling.

Main Results:

• Nb-doped PZT films self-compensate stoichiometry up to 8 mol% Nb with 10 mol% PbO excess.
• Higher Nb concentrations require reduced PbO excess to maintain single-phase perovskite structure (e.g., 13 mol% Nb with 6 mol% PbO excess).
• Nb doping suppresses {100} orientation, lowers Curie temperature, and broadens permittivity peak.
• Multi-phase films (due to excess pyrochlore) degrade dielectric (εr from 1360 to 940) and piezoelectric (d33,f from 112 to 42 pm/V) properties.
• Optimized PbO levels (6 mol%) restore phase purity, enhancing εr to 1330 and d33,f to 106 pm/V.
• Internal bias field magnitude increases with Nb doping, influenced by lead (Pb) and oxygen (O) vacancies.

Conclusions:

• Stoichiometric control via PbO excess is critical for phase-pure perovskite Nb-doped PZT films.
• Optimized Nb-doped PZT films exhibit improved dielectric and piezoelectric properties compared to multi-phase counterparts.
• Nb doping influences charge compensation mechanisms and internal bias field formation, impacting device performance.