Pb2+/Co2+ modified growth and phase transitions of CsPbBr3 in heavy metal oxide glass with enhanced magnetic and magneto-optical properties

Abstract

In this study, we investigated the impact of Pb/Co compositional ratios on the growth and phase transition of CsPbBr3 within PbO-Bi2O3-B2O3 glasses. We employed XRD Rietveld refinement and Raman spectra for a thorough analysis of structural modifications and crystal phases. To assess the morphology, size, and distribution of CsPbBr3 crystals, as well as the homogeneity of embedded glasses, we utilized SEM and TEM, along with SAED patterns. The results confirmed a phase transition from cubic CsPbBr3 to tetrahedral CsPb2Br5 at Pb content exceeding 60%, leading, however, to severe crystallization and the transformation of glassy phases into ceramics. Expanding on the optimal 45% PbO content, we also explored the influence of CoBr2. XRD refinement and Raman analysis revealed Co content-dependent growth and phase transition of CsPbBr3 within the glasses. XPS studies demonstrated the coexistence of Co2+ and Co3+ ions, and their spin states and coordination were verified through XANES and EPR analysis. Notably, the presence of high-spin octahedral Co2+ replacing Pb in the B-site of perovskite resulted in observed ferromagnetism in the Co-doped glasses. Magnetization increased within the 1–3% Co content range. Simultaneously, a high-value Verdet constant of 108 rad/T·m at 633 nm was obtained, presenting an attractive feature for diamagnetic glasses.