@article{Zhang2026, 
author = {Hanyu Zhang and Xiaona Jiang and Qifan Li and Chuanjian Wu and Ke Sun and Zhongwen Lan and Zhong Yu},
title = {Interfacial engineering in heterogeneous NiCuZn ferrite/(Mg,Ca)TiO3 ceramic composite circulator substrates},
year = {2026},
journal = {Journal of Advanced Ceramics},
volume = {15},
number = {1},
pages = {9221197},
keywords = {interface, co-firing, calcium magnesium titanate ceramic, glass brazing, NiCuZn ferrite (NCZF)},
url = {https://www.sciopen.com/article/10.26599/JAC.2025.9221197},
doi = {10.26599/JAC.2025.9221197},
abstract = {Heterogeneous nested composite substrates significantly enhance circulator performance over single-ferrite substrates. This study establishes two distinct interface engineering strategies, diffusion-suppressed co-firing and mechanically interlocking brazing, for the fabrication of robust NiCuZn ferrite (NCZF)/(Mg,Ca)TiO3 (MCT) joints, overcoming the limitations inherent to conventional adhesive bonding. The addition of low-melting-point ZnO–B2O3–SiO2 (ZBS) tailored the sintering behavior and dielectric properties of MCT, enabling co-firing with NCZF at 1050 °C. Thermal shrinkage adjustment effectively suppresses ion interdiffusion driven by compressive stresses from radial extrusion of the outer ring contraction, and the width of the transition region is just 29 μm. Subsequently, brazed substrates were fabricated on the basis of the wettability of the La2O3–CaO–ZnO–B2O3–SiO2 (LCZBS) glass. The ceramic boundaries undergo localized dissolution by the erosive interaction of molten glass, whereas the width of the brazing seam increases with brazing temperature (Tb), with the narrowest transition region of 30 μm. Ti4+ ions from MCT diffused through the glass network, forming a ZnO–TiO2 enrichment interfacial layer at the NCZF boundary. Moreover, the Mg2TiO4 whiskers grow into the solder region through in situ reactions at the MCT interface, forming a mechanically interlocked architecture. This structure serves as the primary contributor to the superior shear strength of brazed substrates relative to co-fired substrates. By elucidating the distinct interfacial regulatory mechanisms in co-firing and brazing, this study establishes a foundation for precision interface design in high-reliability composite substrates, supporting the development of high-performance circulators for microwave applications.}
}