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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]

We use reaction sintering method (RS) to prepared 0.85(1 − xCaTiO3−xLnAlO3)–0.15Ca1.15Ln0.85Al0.85Ti0.15O4 (Ln = Nd, Y) ceramics. CLnC ceramics have two phase structures of perovskite and K2NiF4. The ceramic grains are obvious solid solutions, and gradually enlarge with increasing the sintering temperature. CNdC ceramics exhibit good microwave dielectric properties in the sintering temperature range of 1475–1575 °C. As the sintering temperature increases from 1475 to 1500 °C, the density of CNdC ceramics tends to be stable, fluctuates around 4.6 g/cm3. The εr reaches maximum value at 1500 °C then gradually decreases. As the sintering temperature increases from 1500 to 1550 °C, the Q × f keeps a stable value from 41,953 to 44,188 GHz. As the sintering temperature was 1500 °C, the CNdC ceramics achieved the best microwave dielectric properties with εr = 37.15, Q × f = 44,188 GHz, τf = − 4 ppm/°C. The sintering temperature of CYC ceramics was relatively low and the ceramics sintered at 1450 °C achieved good microwave dielectric properties of εr = 38.3, Q × f = 29,620 GHz, τf = 0.03 ppm/excellent. It is worth noting that CYC ceramics have an excellent τf, which can ensure excellent temperature stability during 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]