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Ca 1.15 RE 0.85 Al 0.85 Ti 0.15 O 4 (RE = Nd, La, Y) ceramics were prepared by a reaction sintering method. The sintering behavior, phase composition, microstructure and microwave dielectric performances of ceramics were investigated. X-ray diffraction patterns illustrated that both the Ca 1.15 Nd 0.85 Al 0.85 Ti 0.15 O 4 (CNAT) and Ca 1.15 Y 0.85 Al 0.85 Ti 0.15 O 4 (CYAT) ceramics are single-phase structures, and the Ca 1.15 La 0.85 Al 0.85 Ti 0.15 O 4 (CLAT) ceramic contain LaAlO 3 and CaO phases. The apparent morphology and elemental distribution of the ceramic samples were analyzed by using scanning electron microscope and energy dispersive spectrometer. When the sintering temperature is 1500 °C, the CNAT and CYAT ceramics have the best microwave dielectric properties with ε r = 19.2, Q × f = 74924 GHz, τ f = −1.21 ppm/°C and ε r = 17.5, Q × f = 27440 GHz, τ f = −5.79 ppm/°C, respectively. And the best microwave dielectric properties of ε r = 17.5, Q × f = 22568 GHz, τ f = −14.69 ppm/°C were obtained for the CLAT ceramic sintered at 1525 °C. The reaction sintering method provides a low-cost, economical and straightforward method for the preparation of the Ca 1.15 RE 0.85 Al 0.85 Ti 0.15 O 4 (RE = Nd, La, Y) ceramics, which has promising potential for application. [ABSTRACT FROM AUTHOR]

Novel NaAGeO 4 (A = Sm, Y) ceramics with olivine structures were prepared and characterized. The phase composition, microstructural evolution, and densification behavior of the ceramics were investigated. The NaAGeO 4 (A = Sm, Y) ceramics possessed a single orthorhombic crystal system with Pbn21 and Pnma space groups. The NaSmGeO 4 ceramics had dense grains, clear boundaries, and low sintering temperatures, whereas a relatively wide range of sintering temperatures were feasible for the NaYGeO 4 ceramics. The NaSmGeO 4 ceramic material sintered at 1025 °C possessed excellent performance-related parameters, i.e., Q × f = 31,281 GHz, ε r = 6.29, and τ ƒ = −48.3 ppm/°C, whereas those for the NaYGeO 4 ceramic material were Q × f = 32,646 GHz, ε r = 6.74, and τ ƒ = −39 ppm/°C at 1200 °C. Furthermore, doping the NaYGeO 4 ceramic material with CaTiO 3 to obtain 0.12CaTiO 3 -0.88NaYGeO 4 yielded a τ ƒ value close to zero (−3 ppm/°C). The results demonstrate that NaAGeO 4 (A = Sm, Y) ceramics have substantial potential for application in microwave devices. [ABSTRACT FROM AUTHOR]

Novel 0.695CaTiO 3 -0.305SmAlO 3 + x wt% CeO 2 (x = 0, 0.5, 1.0, 1.5) ceramics were fabricated using a reaction-sintering (RS) approach. The crystal structure, morphology, and microwave dielectric properties of ceramics were systematically studied. The addition of CeO 2 could effectively improve the sintering behavior of 0.695CaTiO 3 -0.305SmAlO 3 (CTSA) ceramics. When x = 0.5 wt%, the ceramics exhibited optimal microwave dielectric properties, with ε r = 43.9, Q × f = 48 779 GHz, and τ ƒ = −0.24 ppm/°C, thereby indicating that the samples prepared via the RS route possess superior dielectric properties compared to those prepared by the conventional solid phase reaction. The results demonstrate that CaTiO 3 -SmAlO 3 ceramics can be prepared simply and efficiently through a reaction-sintering process. [ABSTRACT FROM AUTHOR]