Three different series of lead-free ceramics, i.e., (1-y)Bi_1.03(1-x)La_xFeO₃–yBaTiO₃ (y = 0.27, x = 0.00–0.12), (y = 0.30, x = 0.00–0.10), and (y = 0.33, x = 0.00–0.08) are prepared via a conventional solid-state reaction with water quenching. From X-ray diffraction and electrical property measurements, two morphotropic phase boundaries (MPBs) are discovered in all three ceramic systems. The first MPB (MPB-I) appeared between rhombohedral and tetragonal phases, whereas the second MPB (MPB-II) appeared between tetragonal and cubic-like phases. The highest direct piezoelectric coefficients (d₃₃ = 201, 274, and 268 pC/N) are mainly attributed to the typical MPB-I of the rhombohedral and tetragonal phases. However, the highest converse piezoelectric coefficients (d₃₃∗ = 490, 500, and 570 pm/V with Curie temperature > 330 °C) are obtained for compositions near to the MPB-II. A significant enhancement in the dielectric constant at low temperature is associated with the local structural heterogeneity by La³⁺ doping, which serves as an origin for a high piezoelectric strain response. Based on the crystal structure as well as on the dielectric, ferroelectric, and piezoelectric properties, a phase diagram is constructed for La-doped BiFeO₃BaTiO₃ ceramics. This phase diagram reveals the relationship between piezoelectric performance and crystal structure.

三种不同系列的无铅陶瓷，即（1-y）Bi _{1.03（1- x）} La _x FeO ₃ - y BaTiO ₃（y  = 0.27，x  = 0.00-0.12），（y  = 0.30，x  = 0.00–0.10）和（y  = 0.33，x = 0.00–0.08）是通过常规的固态反应和水淬制备的。通过X射线衍射和电性能测量，在所有三个陶瓷系统中都发现了两个同相相界（MPB）。第一个MPB（MPB-I）出现在菱形和四方相之间，而第二个MPB（MPB-II）出现在方形和立方相之间。最高的直接压电系数（d ₃₃  = 201、274和268 pC / N）主要归因于菱形和四方相的典型MPB-I。但是，最高的逆压电系数（d ₃₃对于接近MPB-II的成分，获得∗ = 490、500和570 pm / V，居里温度> 330°C）。低温下介电常数的显着提高与La ³⁺掺杂引起的局部结构异质性有关，La ³⁺掺杂是高压电应变响应的起因。基于晶体结构以及介电，铁电和压电特性，构建了La掺杂BiFeO ₃ BaTiO ₃陶瓷的相图。该相图揭示了压电性能与晶体结构之间的关系。