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Structural and Dielectric Evolution of Nb-Doped High-Entropy Perovskite Ceramics With Near-Zero τf
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DOI：10.1111/jace.70993.png)
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Abstract
En 中文
Nb2O5-doped (Ca0.6La0.1Nd0.1Sm0.1Y0.1)(Ti0.6Al0.4)O3 (CLNSYTA) high-entropy ceramics (0.06–0.10 Nb) were synthesized via a solid-state reaction. x-Ray diffraction and aberration-corrected transmission electron microscopy confirmed the formation of an orthorhombic main phase (Pbnm), accompanied by a pyrochlore-type secondary phase. The Nb5+ solubility limit was x = 0.09, corresponding to a unit cell volume of 227.64 Å3. x-Ray photoelectron spectroscopy analysis revealed that Nb5+ doping increased the Ti3+/Ti4+ ratio, indicating that oxygen vacancy formation associated with [TiO6] octahedra was the primary mechanism controlling the variations in the quality factor (Q × f: 13 000–18 000 GHz). Nb5+ substitution significantly increased the relative permittivity (εr) from 17.62 to 42.80 and optimized the temperature coefficient of resonant frequency (τf) from −8.83 to −0.18 ppm/°C. All samples exhibited excellent dielectric stability, with temperature coefficient of capacitance values of < 15% at temperatures up to 450°C. Simulation results for a microstrip patch antenna based on the x = 0.09 ceramic substrate revealed a simulated return loss (S11) of −20.88 dB and a peak gain of 1.19 dBi at 1.44 GHz. This study provides insights into the defect chemistry and polarization mechanisms of high-entropy perovskite ceramics for microwave applications.
Keywords:
high-entropy perovskite ceramics
lattice distortion
microstrip patch antenna
microwave dielectric properties
oxygen vacancies
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