Enhanced dielectric properties of CaLnNbWO8 (Ln = La, Nd, Sm, Gd, Ho) through an entropy engineering strategy

Abstract

The advancement of dielectric ceramics with a low dielectric constant (ε_r), high quality factor (Q × f), and near-zero temperature coefficient of resonant frequency (τ_f) is crucial for optimizing the performance of microwave devices. Although significant progress has been made in the development of low ε_r microwave dielectric ceramics, achieving an optimal balance among these three key parameters remains a challenge. Herein, CaLnNbWO₈ (Ln = La, Nd, Sm, Gd, and Ho) ceramics were synthesized using a solid-phase reaction method, and the effects of entropy engineering on their crystal structure and microwave dielectric properties were systematically investigated. The results demonstrate that the entropy effect minimizes extrinsic losses by suppressing porosity and secondary phases, thereby enhancing the intrinsic Q × f through improved structural homogeneity. Additionally, the strengthening of W–O bonding energy contributes to enhanced thermal stability. The optimized Ca(LaNdSmGdHo)_1/5NbWO₈ (5CLnNWO) ceramics exhibit outstanding microwave dielectric properties (ε_r = 17, Q × f = 46 596 GHz at 10 GHz and τ_f = 11.74 × 10⁻⁶ °C⁻¹). This study provides a novel strategy for designing high-entropy scheelite ceramics with superior dielectric performance, offering valuable insights for future material development for microwave applications.