Al2O3 tailored La0.8Sr0.2FeO3 crystallization in heavy metal oxide glass: Synthesis, structure, and enhanced linear & nonlinear properties

Glass containing magnetic nanocrystals are attractive to provide high optical linear and nonlinearity properties. In this study, we reported the synthesis of perovskite La _0.8Sr _0.2FeO ₃ nanocrystals in heavy metal oxide glass under the Al ₂O ₃ tailoring. The influence of Al ₂O ₃ amount to the formation of La _0.8Sr _0.2FeO ₃ nanocrystals and the influence of nanocrystals to glass structure, optical linear& nonlinear properties were thoroughly investigated. The 10 nm-nanocrystals of orthogonal La _0.8Sr _0.2FeO ₃ were synthesized by melting quenching followed with subsequent crystallization process at 400 °C for 30 min under the tuning of Al ₂O ₃. The formed La _0.8Sr _0.2FeO ₃ were well distributed in matrix without aggregation. Structure and chemical valence study revealed the aluminum abnormality effect and the Sr ²⁺ induced multi-valence states of Fe ions and oxygen vacancies in La _0.8Sr _0.2FeO ₃ lattice. Such modification clearly influenced the optical absorption, refractive index, polarizability, energy band gap shrinkage and nonlinearity. Physical parameters such as oxygen packing density, free volume etc. were calculated to confirm the influence of Al ₂O ₃ tailored La _0.8Sr _0.2FeO ₃ crystallization to glass. The glass with 10%Al ₂O ₃ amount exhibited a large thermal stability (132 °C), low thermal expansion coefficient (10.2 ×10 ^-6/K) and high BO ₄/AlO ₄ units, providing suitable environment for La _0.8Sr _0.2FeO ₃ crystallization. About 20 nm nanocrystals were formed and well distributed in glass which contributed to large nonlinearity absorption coefficient (5.19 ×10 ⁻¹⁰ m/W) and FOM (13.6 ×10 ³ esu cm) which much superior than from relative literatures. The obtained glass with extremely good optical linear and nonlinearity performances can be promising candidate for photonics device applications.