Phase evolution, P-V-L chemical bond calculation, and optimized microwave dielectric properties of Ca²⁺-modified NaSrCeMo₃O₁₂ scheelite ceramics sintered at low temperature
Year: 2026
Type: preprint
Abstract: A series of newly developed Na(Sr₁₋ₓCaₓ)CeMo₃O₁₂ (x = 0.02–0.08) microwave dielectric ceramics with tetragonal scheelite framework were successfully prepared via the conventional solid-state sintering route. The modulation effects of Ca²⁺ iso-valent substitution on crystal structural evolution, densification progress, microstructural morphology and microwave dielectric performances were systematically explored. X-ray diffraction characterization combined with Rietveld full-profile refinement validated that all designed compositions formed a pure tetragonal scheelite phase belonging to the I4₁/a space group, where Ca²⁺ ions were effectively doped into the Sr²⁺ lattice sites. This substitution behavior triggered a gradual linear reduction in unit cell volume, which is attributed to the smaller ionic radius of 1.12 Å for Ca²⁺ compared with 1.26 Å for the replaced Sr²⁺ ions. Scanning electron microscopy observations demonstrated that fully compact, pore-free and uniform microstructures could be achieved at a relatively low optimized sintering temperature of 900°C. Impressively, the specimen with x = 0.04 delivered outstanding comprehensive microwave dielectric performances: a low dielectric permittivity (ε r ) of 10.9, an ultra-high quality factor (Q × f) of 125265 GHz, and a temperature coefficient of resonant frequency (τf) of -40.059 ppm/°C. Combined analysis of Raman spectroscopy and P–V–L chemical bond theory revealed that the Mo–O covalent bond plays a decisive role in governing the intrinsic dielectric loss of the system, and the remarkable elevation of Q × f value at x = 0.04 is fundamentally derived from the simultaneous promotion of atomic packing fraction and lattice energy. This study proves that Ca-modified NaSrCeMo₃O₁₂ ceramics are highly competitive candidate materials for ultra-low temperature co-fired ceramic (ULTCC) applications in advanced millimeter-wave communication systems.
Source: Research Square
Authors: Ruoxi Chen, Yuan-Bin Chen
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225782663