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The electronic structure and optical properties of orthorhombic Ce0.7Nd0.3AlO3 under different pressures are studied with the Heyd-Scuseria-Ernzerhof screened hybrid functional. With the increase of pressure, both the lattice constants and the band gap show a decreasing trend. The pressure not only reduces the bandwidth of the middle and high valence bands but also increases the strength of the density of states. The main peak of the imaginary part of the dielectric constant and the static dielectric constant increase continuously with the increasing pressure. The blue-shift of prominent peaks of absorption coefficient, reflectivity, and energy-loss energy are obvious with the increasing pressure. [ABSTRACT FROM AUTHOR]

The original magnesium titanate powders were pre-sintered, and the 0.95MgTiO3-0.05CaTiO3 (95MCT) ceramics were prepared by the pre-sintered magnesium titanate showed better dielectric properties than by the original powders. Because the magnesium titanate (MgTi2O5) phase was not detected. Then the microwave patch antenna was designed by the prepared ceramic measured at 2.8 GHz exhibited a 4.83% bandwidth (return loss ≤ −3 dB) of the center frequency. [ABSTRACT FROM AUTHOR]

The crystal structure evolution and microwave (MW) dielectric properties of xCa(Al0.5Nb0.5)O3+(1− x)SrTiO3 ( xCAN+(1− x)ST, 0≤ x≤1.0, ) dielectric ceramics were investigated. X-ray diffraction patterns illustrated that a single perovskite solid solution could be formed between the two end members; however, minor amount of pyrochlore phase was also detected in the composition range of 0.5≤ x≤0.9. With the increase of x value, the crystal structure gradually evolved from a simple Pm3 m cubic to a monoclinic P21/ n space group with the octahedral tilting and the B-site ordering structure transition subsequently developed. The MW dielectric properties of xCAN+(1− x)ST solid solutions were elaborately investigated and correlated to their crystal structures. The microscopic structure-related thermal parameters in the xCAN+(1− x)ST solid solution were analyzed in terms of the Claussius-Mossotti equation to reveal the original contributors in temperature coefficients. Temperature coefficient-compensated ceramic could be obtained in the xCAN+(1− x)ST system in the range of 0.5< x<0.6. When sintered at 1500°C for 4 h, a dielectric constant ℇr of 37.32, a Qf product of 25 430 GHz, and a τf value of −22.4 ppm/°C MW dielectric ceramic could be obtained in the 0.6Ca(Al0.5Nb0.5)O3+0.4SrTiO3 composition. [ABSTRACT FROM AUTHOR]