Synthesis, structure and properties of nanoparticles based on SrFe12-xRxO19 (R = Er, Tm) compounds.

• Dissolution of rare-earth elements (REE) in strontium hexaferrite SrFe 12-x R x O 19 (where R = Er, Tm) obtained by the mechanochemical synthesis was investigated and has value of × = 0.08. • Hexaferrites SrFe 12-x R x O 19 (where R = Er, Tm) doped by REE with the × = 0.08 were obtained by the citrate method. • Colloidal aqueous solutions of strontium hexaferrite nanoparticles doped by REE (Er, Tm) and synthesized by citrate method were obtained by high-energy ball milling (50 h) in octadecene solution with oleic acid. • The dynamic light scattering data show that the volume of the synthesized particles is in the range up to 150 nm, which is suitable for using the synthesized nanoparticles for biomedical applications. • For the first time the hexaferrite SrFe 12-x R x O 19 (where R = Er, Tm) nanoparticles were evaluated as MRI contrast agents. In this work a comprehensive analysis of the structure and properties of doped SrFe 12-x R x O 19 (R = Er, Tm) hexaferrites has been studied. The hexaferrtes were synthesized by two methods: mechanochemical and citrate approaches. The solubility of rare-earth elements (REE) has been studied by precision determination of the lattice spacings and cell volume of the samples, synthesized by mechanochemical method. It has been shown that the solubility of Er and Tm at a temperature of 1200 °C does not exceed × = 0.08 REE ions per formula unit. According to Mössbauer spectroscopy, REE atoms preferentially occupy 12k positions. Nanoparticles of SrFe 12-x R x O 19 (R = Er, Tm) compounds for MRI were obtained by high-energy ball milling of the citrate samples for 50 h in an octadecene solution with oleic acid. Stable hydrosols of nanoparticles were obtained after their coating with Pluronic F127 polymer. It has been shown that the obtained nanoparticles can be used for biomedical applications as contrast agents. [ABSTRACT FROM AUTHOR]