Effect of Mn Addition on the Mechanical Properties and Ferroelectric Behavior of Bi0.5Na0.5TiO3 and 94(Bi0.5Na0.5TiO3)–6(BaTiO3) Ceramics

The effect of Mn addition on the structural, dielectric, ferroelectric, and mechanical properties of Bi0.5Na0.5TiO3 (BNT) and 0.94(Bi0.5Na0.5TiO3)–0.06(BaTiO3) (BNT–BT) ceramics was systematically investigated under identical processing conditions. Powders were calcined at 750 °C for 2 h and 900 °C for 2 h, followed by sintering at 1060 °C for 5 h. Mn contents of 0.5 and 5 mol% were selected to represent low-level substitution and near-saturation regimes. XRD confirmed single-phase perovskite formation within laboratory detection limits, while Raman spectroscopy revealed Mn-induced lattice distortions. Low Mn addition (0.5 mol%) enhanced densification and improved remanent polarization in BNT–BT (Pr = 33.5 μC/cm2). In contrast, 5 mol% Mn promoted grain coarsening, increased porosity, and reduced functional performance. Mechanical properties evaluated using two-parameter Weibull statistics showed composition-dependent variations in characteristic hardness and elastic modulus. The results demonstrate that Mn-doping effects depend strongly on both dopant concentration and host-lattice structural state, distinguishing beneficial substitution from defect-saturation behavior in lead-free BNT-based ceramics.