Effect of progressive substitution of Lu by Ho on the structural and dielectric properties of nanocrystalline LuFeO3 orthoferrite. (January 2022)

• Record Type: Journal Article
• Authors: Leelashree, S.; Kaul, S.N.; Srinath, S.
• Is Part Of: Materials research bulletin. Volume 145(2022)
• Publication Date: 2022-01
• Subjects: LuFeO3 -- HoFeO3 -- Rare-earth orthoferrites -- Raman scattering -- Hydrothermal synthesis; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2021.111570
• Languages: English
• ISSNs: 0025-5408

Abstract

Highlights: In hydrothermally synthesized nanocrystalline Lu1-x Hox FeO3 ( x = 0 to 1), as small as 5% Ho solute concentration suffices to stabilize orthorhombic structure at the cost of hexagonal structure prevalent in the LuFeO3 host. Two new Raman modes, observed at wave numbers ≈ 53 cm −1 and ≈ 69 cm −1 in all the compositions (0 ≤ x ≤ 1) in nanocrystalline Lu1- x Ho x FeO3, have their origin in the breaking of translation symmetry at the surfaces/interfaces/grain boundaries of the nanocrystalline particles. The observed functional dependence of Raman mode wave numbers on the Ho concentration is directly correlated with the change in respective bond lengths. The RA soft mode Ag (3) and Ag (5) wavenumber increases linearly with the FeO6 octahedra tilt angle φ [ 010 ] and θ [ 101 ], respectively, indicating that these modes are independent and sensitive to orthorhombic distortion. The real (ε') and imaginary (ε") parts of the complex dielectric permittivity, measured at room temperature over the ac electric-field frequency range, 20 Hz ≤ f ≤ 2 MHz, unravel two different types of dielectric relaxation in nanocrystalline Lu1-x Hox FeO3 . Abstract: We report the results of an extensive structural, Raman scattering and dielectric investigation of nanocrystalline Lu1- x Ho x FeO3 (0 ≤ x ≤ 1) orthoferrite, synthesized by the hydrothermal method. The Raman modes specific to the rotation of FeO6 octahedra assert that 5 at.% Ho solute concentration suffices to stabilize the orthorhombic structure in the LuFeO3 host. We observed two new Raman modes at ≈ 53 and ≈ 69 cm −1 in all the compositions. The Raman mode Ag (3) [Ag (5)] wavenumber increases linearly with the FeO6 octahedra tilt angle φ[010] [θ[101] ], indicating that these independent modes are sensitive to orthorhombic distortion. The real (ε'), imaginary (ε") parts of the complex dielectric permittivity, measured at room temperature over the ac electric-field frequency range, 20 Hz ≤ f ≤ 2 MHz, unravel two different types of dielectric relaxation in nanocrystalline Lu1-x Hox FeO3 . Graphical abstract: Image, graphical abstract