Dielectric, impedance, and modulus spectroscopic studies of lanthanum-doped nickel spinel ferrites NiLaxFe2-xO4 nanoparticles

• Published in: Journal of sol-gel science and technology 2022-03, Vol.101 (3), p.596-605
• Main Authors: Mustafa, Ghulam, Khalid, Muhammad, Chandio, Ali Dad, Shahzadi, Kiran, Uddin, Zaheer, Khan, Junaid Kareem, Channa, Naimat Ullah, Gilani, Zaheer Abbas, Noor ul Huda Khan Asghar, H. M.
• Format: Article
• Language: English
• Subjects: Ceramics; Chemistry and Materials Science; Combustion; Composites; Crystallites; Dielectric loss; Dielectric properties; Doping; Electrical properties; electronic; Face centered cubic lattice; Frequency ranges; Glass; Grain boundaries; Impedance; Inorganic Chemistry; Lanthanum; Lattice parameters; Lattice strain; magnetic and ferroelectric applications; Materials Science; Microstrain; Microwave frequencies; Nanoparticles; Nanotechnology; Natural Materials; Nickel ferrites; Optical and Electronic Materials; Original Paper: Sol-gel and hybrid materials for dielectric; Permittivity; Sol-gel processes; Spinel; Synthesis; X-ray diffraction
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-020-05359-z

A series of lanthanum (La)-doped nickel (Ni) ferrites NiLa x Fe 2- x O 4 with doping concentrations ( x  = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) is synthesized via a sol–gel auto-combustion method. Structural properties are determined with the help of X-ray diffraction (XRD). The effect of La doping on dielectric properties of Ni ferrites is discussed. XRD analysis confirms the existence of pure FCC spinel phase, and no impurity phase was detected. The lattice constant decreases initially due to strain produced by La 3+ ions replacement. At higher doping concentrations, the lattice constant increases due to the large ionic radius of La 3+ as compared to Fe 3+ . Tangent loss (tan δ ), dielectric constant, and dielectric loss values are determined in the 1 MHz to 3 GHz frequency range, and explained by the Maxwell–Wagner model. A persistent behavior of dielectric loss and dielectric constant was found in the mid microwave frequency region. The most stable behavior of the dielectric constant ( ε ′) and dielectric loss ( ε″ ) in the high-frequency region is found with ( x  = 0.04). Ac conductivity is also discussed in the 1 MHz to 3 GHz region, and is found to be impacted by grain and grain boundary resistive behavior at low and high frequencies. Cole–Cole plots of different samples, corresponding to different doping concentrations, are used to describe the conduction phenomena. The stable response of dielectric constant ( ε ′) and dielectric loss ( ε″ ) in the mid microwave frequency region makes NiLa x Fe 2- x O 4 nanoparticles a potential candidate for microwave devices. Highlights Lanthanum-doped nickel ferrites nanoparticles were successfully synthesized by sol–gel auto-combustion method. The effect of lanthanum doping in nickel ferrites on structural and electrical properties was investigated. The structural parameters such as lattice constant, crystallite size, lattice strain, microstrain were determined. Frequency-dependent dielectric, impedance, and electric modulus properties were investigated in microwave region. Ac conductivity in microwave region was also investigated.