A morphotropic phase boundary (MPB) between rhombohedral (R) and tetragonal (T) phases was identified in a few (0.9-x)NaNbO₃-0.1BaTiO₃-xABO₃ (x = 0–0.05) lead-free systems. Critical roles of R-phase inducers were specially evaluated in terms of phase boundary position, microstructure and piezoelectric responses. The results indicate not only the tolerance factor of the ABO₃ additive but also its ferroelectricity and corresponding volume change would influence the formation of phase boundary and further determine dielectric and ferroelectric responses. The piezoelectric coefficient d₃₃ of MPB compositions was compared with theoretically-calculated d_33-cal according to d₃₃ = 2P_r·ε₃₃·Q₃₃, demonstrating that the piezoelectric response of these systems should be determined by combined effects of the phase coexistence, nano-scale domains and particularly enhanced dielectric responses. The largest d₃₃ ∼305 pC/N, the highest ε₃₃^T/ε_o ∼2815 and the lowest P_r ∼14.7 μC/cm² were achieved in the MPB composition with 3.75% SrZrO₃. These experimental results provide a valuable reference for designing new NaNbO₃-based lead-free piezoelectric materials.

在一些（0.9-x）NaNbO ₃ -0.1BaTiO ₃ -xABO ₃（x = 0-0.05）无铅系统中，菱形（R）和四方（T）相之间的相变相界（MPB）被确定。根据相界位置，微观结构和压电响应，对R相感应器的关键作用进行了专门评估。结果表明，不仅ABO ₃添加剂的耐受因子，而且其铁电性和相应的体积变化都将影响相边界的形成，并进一步确定介电和铁电响应。根据d将MPB组合物的压电系数d ₃₃与理论计算的d _33-cal进行比较₃₃  = 2P _{- [R} ·ε ₃₃ ·Q ₃₃，表明这些系统的压电响应应该由相共存的综合作用下，纳米尺度的域，特别是增强的介电响应而确定。最大d ₃₃ ~305 PC / N，最高ε ₃₃ ^Ť /ε _ö ~2815和最低的P _{- [R} ~14.7μC/厘米²在MPB组成分别实现与3.75％SrZrO ₃。这些实验结果为设计新型基于NaNbO ₃的无铅压电材料提供了有价值的参考。