Crystallographic Profiling, Core-Shell Electronic Configurations, and Investigations of Frequency-Dependent Dielectric Characteristics of Sb2O3-V2O5 Micro Ceramics

Abstract

A series of V_2-xSb_2xO_5-δ (Sb-V-O) ceramic powder samples with molar concentrations ranging from 0.05 to 0.08 were synthesized using a solid-state reaction method. Crystallographic analysis conducted through Rietveld refinement indicates that at a molar fraction of x=0.05, the orthorhombic V₂O₅ phase is observed. Conversely, at molar concentrations of x=0.06, 0.07, and 0.08, the orthorhombic phase of V₂O₅ and the tetragonal phase of SbVO₄ are present simultaneously. X-ray photoelectron spectroscopy (XPS) was employed to ascertain the elemental oxidation states, revealing the presence of V⁵⁺, V⁴⁺, Sb³⁺ ions, and Sb⁰ metal atoms, along with O1s photoelectron peaks. The photoluminescence (PL) emission spectrum suggests transitions from a shallow donor level to the valance band. The room temperature AC conductivity and dielectric property results reveal a systematic decrease in the dielectric constant. The AC conductivity experimental data was accurately modeled using the Almond-West formalism, yielding high R² values (0.9968–0.9986) and low chi-square errors (1.157×10⁻¹¹–9.42×10⁻¹²) obtaining hopping frequency values for each composition (x = 0.05–0.08). AC conductivity (σ_ac) decreased from 5.08×10⁻⁴ S/m to 2.40×10⁻⁴ S/m at 10 MHz, while DC conductivity (σ_dc) dropped from 7.22×10⁻⁵ S/m to 1.55×10⁻⁵ S/m. This reduction in conductivity is attributed to structural changes from Sb³⁺ substitution, which disrupts polaronic conduction by reducing the number of available O²⁻ ions and promoting SbVO₄ phase formation, hindering charge transport. The Sb₂O₃-V₂O₅ ceramics exhibit promising potential for energy storage applications, particularly in capacitors requiring high dielectric constants at low frequencies. At lower frequencies, grain boundaries inhibit conduction, enhancing dielectric constant values; at elevated frequencies, grain conduction predominates, lowering dielectric constant in accordance with Koop’s phenomenological theory, favoring applications in multi-layer ceramic capacitors. A notably higher dielectric loss factor (εr'') at low frequencies (10 Hz–1 kHz) indicates lossy behavior, beneficial for microwave absorption, while its stabilization above 10 kHz suggests minimal energy dissipation, ideal for high-frequency electronic and dielectric devices.