| Summary: | A series of charge-balanced Si<sup>4+</sup>-M<sup>1+,2+</sup> (M = Mg<sup>2+</sup>, K<sup>+</sup>, Li<sup>+</sup>) substitution compositions with the chemical formulae of SrFe<sub>12−2<i>x</i></sub>Si<i><sub>x</sub></i>Mg<i><sub>x</sub></i>O<sub>19</sub> (<i>x</i> = 0, 0.05, 0.1, 0.2), Sr<sub>1−<i>y</i></sub>Fe<sub>12−<i>y</i></sub>Si<i><sub>y</sub></i>K<i><sub>y</sub></i>O<sub>19</sub> (<i>y</i> = 0.05, 0.1, 0.2), and SrFe<sub>12−<i>z</i></sub>(Si<sub>0.6</sub>Li<sub>0.6</sub>)<i><sub>z</sub></i>O<sub>19</sub> (<i>z</i> = 0.05, 0.1, 0.2, 0.4, 0.6) were prepared using conventional ceramic processes. While the sole doping of Si with <i>x</i> = 0.1 (SrFe<sub>12−<i>x</i></sub>Si<i><sub>x</sub></i>O<sub>19</sub> (<i>x</i> = 0.1)) causes a noticeable Fe<sub>2</sub>O<sub>3</sub> phase formation, the co-doping of Si-Mg and Si-Li allow a single M-type phase formation with x up to <i>x</i> = 0.1 and <i>z</i> = 0.4, respectively. Notably, a 2.6% increase in the saturation magnetization was obtained for Si-Li-substituted SrM with <i>z</i> = 0.05—that is, SrFe<sub>11.95</sub>Si<sub>0.03</sub>Li<sub>0.03</sub>O<sub>19</sub>. Enhancement of the magnet performance can also be achieved when anisotropic permanent magnets are fabricated based on the substitution composition SrFe<sub>11.95</sub>Si<sub>0.03</sub>Li<sub>0.03</sub>O<sub>19</sub>. The remnant magnetic flux density was improved by 2.5% compared to that of the unsubstituted SrM (from 4207 to 4314 G). The maximum energy product (BH<sub>max</sub>) value also increased from 4.24 to 4.46 M·G·Oe. The enhancement in permanent magnet performance is attributed to the increase in the M<sub>S</sub> of SrM by the optimal Si-Li substitution. This is a promising result because enhanced permanent magnet performance is achieved with intrinsic magnetic property improvement.
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