Orthogonal Design Optimisation of the Sintering Process for MnZn Ferrites with Step-Sintering Verification

MnZn ferrites for power electronics require a well-controlled sintering window to balance high initial permeability (<i>µ_i</i>) with low power loss (<i>P_cv</i>). Here, an L9 (3³) orthogonal design was employed to quantify the main effects of sintering temperature, holding time, and oxygen partial pressure on <i>µ_i</i> and <i>P_cv</i> within the investigated processing window, enabling rapid mapping of feasible sintering windows. The orthogonal analysis identifies the relative significance of each factor and reveals a clear performance trade-off between <i>µ_i</i> and <i>P_cv</i>. For maximising <i>µ_i</i>, the optimal sintering condition was 1250 °C, 4 h holding time, and 3.5% oxygen partial pressure, yielding a <i>µ_i</i> of 3453 and a <i>P_cv</i> of 466 mW/cm³ at 100 kHz/200 mT. For minimising <i>P_cv</i>, the optimal condition was 1250 °C, 3.5 h holding time, and 5% oxygen partial pressure, resulting in a <i>µ_i</i> of 2678, with <i>P_cv</i> of 400 mW/cm³ at 100 kHz/200 mT and 182 mW/cm³ at 500 kHz/50 mT. Targeted verification together with XRD, SEM grain-size statistics, and magnetic-loss separation were used to strengthen the process-structure-property interpretation. Overall, the orthogonal-screening-plus-verification strategy provides a practical framework for predicting application-relevant performance trends of MnZn ferrites within a defined processing window.