Sintering behavior and microwave dielectric properties of CaTi1-x(Nb1/2Al1/2)xO3

Abstract

CaTi1-x(Nb1/2Al1/2)xO3 with x=0.1-0.5 ceramics were processed through solid state sintering. X-rays diffraction (XRD) patterns of the compositions showed that the samples have orthorhombic crystal structure with symmetry (Pbnm). The symmetry was further confirmed using Raman spectroscopy. A total of 13 Raman modes were detected, which were in agreement with the XRD results. Microstructure analysis of the samples showed porosity in the samples, presumably due to the substitution of Al, having high melting point. As the concentration of Al and Nb increased, relative permittivity (er), quality factor (Q×fo) and temperature coefficient of resonance frequency decreased. Optimum microwave dielectric properties were achieved for the composition x=0.5 sintered at 1650 °C for 8 h i.e., er ~27.09, Q×fo ~17378 GHz and tf ~ -2.5 ppm/°C.

Effects of pH and calcination temperature on gel-combustion synthesizability of BaZr0.8Y0.2O3 perovskite

“…Among the other activities carried out to achieve high density at minimum sintering temperature and time, the BaZr 0.8 Y 0.2 O 3-δ perovskite was sintered by the spark plasma sintering, but the graphite phase was observed in the perovskite structure [54]. It is worth mentioning that dopants and additives have an important role in the sintering of oxide ceramics and their characteristics [55][56][57][58][59]. In this paper, BaZr 0.8-x Sr x Y 0.2 O 3 (x=0, 0.05, 0.1, and 0.15) perovskites are synthesized by the gel-combustion method and then sintered at different temperatures.…”

Impact of bridging oxygens formation on optical properties of Fe3+ doped Li2O–Al2O3–SiO2–TiO2 glasses

“…Analysis of materials structure containing long-range order of crystals is a sort of a routine process. Nowadays there is a diversity of techniques which is being utilized for prediction of crystalline structures such as transmission electron microscopy (TEM), X-ray diffractometry (XRD) and so on [1][2][3][4]. Nevertheless, extraction of data is still in a serious doubt for the amorphous structures due to the short-range order of crystals distributed stochastically in the bulk of samples.…”

Effects of clay and fireclay addition on the properties of magnesia–forsterite–spinel refractories synthesized at different firing temperatures

“…Refractory oxides are ceramics that can be employed for elevatedtemperature applications [1][2][3][4][5]. Magnesia with a melting point of 2800 °C is a member refractory materials that is broadly used for lining the industrial steel and metallurgical furnaces because of its properties like good slag resistance and superior refractoriness [6][7][8][9].…”