High-Permittivity and Low-Loss Microwave Dielectric Ceramics Based on (x)RE(Zn1/2Ti1/2)O3-(1−x)CaTiO3 (RE=La and Nd)

• Published in: Journal of the American Ceramic Society Vol. 94; no. 3; pp. 817 - 821
• Main Authors: Feteira, Antonio, Iddles, David, Price, Tim, Muir, Duncan, Reaney, Ian M.
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.03.2011
• Subjects: Boundaries; Ceramics; Dielectrics; Diffraction; Doping; Microwaves; Neodymium; Resonant frequencies; Tantalum oxides
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2010.04173.x

Compositions based on REZn1/2Ti1/2O3–CaTiO3 (RE=La and Nd), suitable for microwave (MW) applications have been developed by systematically doping the perovskite B site with Ta2O5, Al2O3, and MgO in order to tune the temperature coefficient of the resonant frequency (τf) and improve the MW quality factor (Q ×fr) Optimized compositions, 0.45La(Zn0.395Ti0.385Ta0.01Al0.21)O3–0.55CaTiO3 (LZT‐CT) and 0.32Nd(Zn0.45Mg0.05Ti0.5)O3–0.10NdAlO3–0.58CaTiO3 (NZT‐CT) were prepared by solid‐state reaction and have been characterized. X‐ray diffraction (XRD) and scanning electron microscopy revealed that both compositions were single phase with a bulk microstructure composed of equiaxed grains (∼10 μm). Electron diffraction and XRD demonstrated that, at room temperature, LZT‐CT and NZT‐CT were orthorhombic with space group Pnma, consistent with an a−a−c+ tilt system. Diffraction contrast transmission electron microscopy revealed a complex domain structure consisting of ferroelastic and antiphase domain boundaries. LZT‐CT and NZT‐CT had zero τf, ɛr=49 and 44, Q×fr=29 600 GHz (at 1.957 GHz), and 32 200 GHz (at 1.971 GHz), respectively.