Atta Ullah

Phase, microstructure and microwave dielectric properties of Mg0:95Ni0:05Ti0:98Zr0:02O3 ceramics

Abstract Mg0:95Ni0:05Ti0:98Zr0:02O3 ceramics was prepared via conventional solid-state mixed-oxide route. The phase, microstructure and microwave dielectric properties of the sintered samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vector network analyzer. The microstructure comprised of circular and elongated plate-like grains. The semi quantitative analysis (EDS) of the circular and elongated grains revealed the existence of Mg0:95Ni0:05T2O5 as a secondary phase along with the parent Mg0:95Ni0:05Ti0:98Zr0:02O3 phase, which was consistent with the XRD findings. In the present study, εr ~17.1, Qufo~195855 ± 2550 GHz and τf ~ -46 ppm/K was achieved for the synthesized Mg0:95Ni0:05Ti0:98Zr0:02O3 ceramics sintered at 1325 °C for 4 h.

Phase microstructure evaluation and microwave dielectric properties of (1–x)Mg0.95Ni0.05Ti0.98Zr0.02O3–xCa0.6La0.8/3TiO3 ceramics

All the compositions in the (1−x)Mg0.95Ni0.05Ti0.98Zr0.02O3–xCa0.6La0.8/3TiO3 (0 ≤ x ≤ 0.2) series were fabricated using solid state sintering route. Mg0.95Ni0.05Ti0.98Zr0.02O3 possessed excellent microwave dielectric properties with εr ≈ 17.1, Quf0 ≈ 195855 GHz, and τf ≈ -46 ppm/°C. τf was tuned through zero by mixing with Ca0.6La0.8/3TiO3. In the present study, τf ≈ -2 ppm/°C with εr ≈ 23.9 and high Quf0 ≈ 115870 GHz was achieved for x = 0.15, i.e., for a mixture of 85% Mg0.95Ni0.05Ti0.98Zr0.02O3 and 15% Ca0.6La0.8/3TiO3.

Raman spectroscopy and microwave dielectric properties of Sn substituted SrLa4Ti5O17 ceramics

Abstract SrLa4Ti5−xSnxO17 (0 ≤ x ≤ 2) ceramics were fabricated through solid state ceramic route and their microwave dielectric properties were investigated in an attempt to tune their temperature coefficient of resonant frequency (τf) to zero. The compositions were sintered to single phase SrLa4Ti5O17 and SrLa4Ti4.5Sn0.5O17 ceramics at x = 0 and x = 0.5, and SrLa4Ti4−xSnxO17 along with a small amount of La2Ti2O7 at x = 1. The major phase observed at x = 2 was La2Ti2O7 but along with SrLa4Ti4SnO17 and SrLa4Ti4O15 as the secondary phases. τf decreased from 117 to 23.0 ppm/°C but at the cost of dielectric constant (εr) and quality factor multiplied by resonant frequency (Qufo) which decreased from 65 to 33.6 and 11150 to 4191 GHz, respectively. The optimum microwave dielectric properties, i.e. τf = 38.6 ppm/°C, εr = 45.5 and Qufo = 7919 GHz, correspond to the SrLa4Ti5−xSnxO17 composition with x = 1.

Processing and microwave dielectric properties of Sr5Ta4TiO17 ceramics

Abstract Sr5Ta4TiO17 ceramics was processed via solid state mixed oxide sintering route. X-ray diffraction revealed single phase formation of Sr5Ta4TiO17 ceramics that crystallized into an orthorhombic crystal structure with a space group Pnnm with lattice parameters of a = 5.681 Å, b = 32.542 Å and c = 3.968 Å, refined by the least squares method. The unit cell density (ρth) was 6.71 g/cm3. The microstructure consisted of plate-like grains and the average size was increased from 2 μm to 5 μm with an increase in sintering temperature from 1450 °C to 1575 °C. Optimum microwave dielectric properties, i.e. єr ~ 66,Qufo ~ 8500 GHz and τf ~ 180 ppm/°C, were achieved for Sr5TaTiO17 ceramics sintered at 1550 °C for 4 h.