This report shows that magnetically isotropic and anisotropic compacts of BaFe12O19or SrFe12O19sinter to high density with controlled microstructure in the presence of a liquid phase. The liquid‐phase compositions are in the systemsMO&sngbnd;SiO2andMO&sngbnd;Al2O3&sngbnd;SiO2,M=Ba, Sr. Further, it is shown that systems containingMB2O4as an additional component will give similar results at significantly lower temperatures. The resultant magnetic properties meet or exceed the appropriate magnet industry criteria for hard ferrite magnets.