Solution combustion assisted synthesis of ultra-magnetically soft LiZnTiMn ferrite ceramics

Abstract

Wide practical application and increasing functional requirements for high-frequency ceramics lead to the active search for novel multicomponent ferrites and their synthesis technique. In this paper, a solution-combustion-assisted approach was proposed and realized for the successful production of ultra-magnetically soft LiZnTiMn-ferrite ceramics with advanced electromagnetic performance. Preceramic nanopowders of Li0.28Zn0.16Ti0.41Mn0.10Fe2.05O4 with spinel structure were synthesized via glycine-nitrate combustion at variable Ox/Red ratios (φ = 0.5, 1.0 and 1.5) followed by stabilizing quenching (600 °C, 2 h) and vibrating mill grinding. LiZnTiMn-ferrite-based fine ceramics were produced then using PVA binding (1 wt%), isostatic pressing (400 МPа) and Bi2O3-assisted (0.3 wt%) isothermal sintering (980 °C, 8 h) techniques. As result, a series of LiZnTiMn-ferrite ceramic samples were obtained and their structure was examined in detail using XRD, SEM, EDXS, AAS and ASA methods. It was shown that the Ox/Red ratio of the initial reaction solution is an efficient parameter affecting both crystallite size (26–38 nm) /crystallinity degree (up to 91%) of preceramic LiZnTiMn-ferrite powders and grain size (2.7–9.8 µm) / grain size distribution of resulting fine ceramics. Based on the results of vibration magnetometry it was found that ceramics samples possess the ultra-magnetically soft behavior with Hc = 0.61–0.89 Oe, Mr = 3.62–5.13 emu/g and Ms = 67.23–78.70 emu/g depending on the initial Ox/Red ratio. Besides, results of resonator analysis (100 Hz - 1000 kHz) demonstrate that the dielectric constant of the samples strongly depends on the average grain size and reaches its maximum value (~ 6.4⸱10–4) at 100 Hz for the stoichiometric Ox/Red ratio (φ = 1.0) of reagents, wherein the linewidths of ferromagnetic resonance and resonance of spin waves practically unchanged and are in ranges of 327–344 and 1.43–1.45 Oe, respectively. Thus, it was found that the solution combustion synthesis, adapted for fine ceramics production, provides controlling morphological and structural parameters of the pre-ceramic powders through Ox/Red ratio of initial reagents and as consequence, allows variable magnetic and dielectric characteristics of the resulting ceramic products. Developed ceramic materials can be promising for use as a basis for modern radio-electronic devices of both civil and military use.