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Abstract Ca 0.66 Ti 0.66 Nd 0.34 Al 0.34 O 3 (CTNA) ceramics were prepared by solid-state reaction method and their sintering behavior, microwave dielectric properties, and microstructure were investigated. CTNA ceramics were examined by Raman scattering to reveal the correlation of perovskite structure with the microwave properties. It found that the area of peak A 1g (O) stretch mode reflects the quality factor Q × f value in the perovskite materials. This concludes that the oxygen octahedron plays an important role of the material's microwave performance. Sintering temperature affected the unit cell volume and the lattice parameters of the CTNA ceramics, the grain size distribution, the Gibbs free energy, the thermal expansion coefficient (CTE), and the dielectric properties (ε r , Q × f , τ f). The samples sintered at 1500 °C displayed the best dielectric constant and Q × f , as 44.94 and 41922.22 GHz, respectively. Highlights • The CTNA ceramics were sintered at different temperatures were investigated. • The thermal analysis detailed description of the stages of sintering process. • The unit cell volume is affected by the sintering temperature was confirmed by XRD. • Raman to reveal the correlation of structure with the microwave properties. • Relationship between grain size, Gibbs free energy, CTE, and dielectric properties. [ABSTRACT FROM AUTHOR]

Perovskite ceramics with a formula of Ca 0.7 Ti 0.7 La 0.3 Al 0.3 O 3 (CTLA) were produced through a conventional solid-state reaction procedure following three different La 3+ -doping methods using powders of La 2 O 3 , or La 2 O 3 /Al 2 O 3 powder mixture, or LaAlO 3 . La 3+ doping favored grain growth and densification, affected the grain size distribution, and improved the dielectric properties of the produced sintered CTLA ceramics. The doping methods had a strong influence on these properties. More specifically, doping with La 2 O 3 and La 2 O 3 /Al 2 O 3 resulted in formation of solid solution, while a secondary phase formed in the CTLA ceramics doped with LaAlO 3 , which caused a coarsening of the microstructure and lowered the La 3+ doping effects on the dielectric properties. The experimental results suggest that La 3+ doping improves the dielectric properties of the sintered CTLA perovskite ceramics, which are further enhanced by doping with Al 3+ ions in small amounts. However, further increase of Al 3+ ions content jeopardizes them. [ABSTRACT FROM AUTHOR]