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High‐Permittivity and Low‐Loss Microwave Dielectric Ceramics Based on ( x )RE(Zn 1/2 Ti 1/2 )O 3 –(1− x )CaTiO 3 (RE=La and Nd)
Author(s) -
Feteira Antonio,
Iddles David,
Price Tim,
Muir Duncan,
Reaney Ian M.
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04173.x
Subject(s) - materials science , orthorhombic crystal system , microstructure , perovskite (structure) , crystallography , transmission electron microscopy , scanning electron microscope , diffraction , temperature coefficient , analytical chemistry (journal) , crystal structure , chemistry , optics , nanotechnology , composite material , physics , chromatography
Compositions based on REZn 1/2 Ti 1/2 O 3 –CaTiO 3 (RE=La and Nd), suitable for microwave (MW) applications have been developed by systematically doping the perovskite B site with Ta 2 O 5 , Al 2 O 3 , and MgO in order to tune the temperature coefficient of the resonant frequency (τ f ) and improve the MW quality factor (Q × f r ) Optimized compositions, 0.45La(Zn 0.395 Ti 0.385 Ta 0.01 Al 0.21 )O 3 –0.55CaTiO 3 (LZT‐CT) and 0.32Nd(Zn 0.45 Mg 0.05 Ti 0.5 )O 3 –0.10NdAlO 3 –0.58CaTiO 3 (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 τ f , ɛ r =49 and 44, Q × f r =29 600 GHz (at 1.957 GHz), and 32 200 GHz (at 1.971 GHz), respectively.