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Sr0.6Ca0.4LaAlO4 ceramic was fabricated via solid-state sintering route and the effect of TiO2 addition on its microwave dielectric properties was investigated. Sr0.6Ca0.4LaAlO4 formed as the major phase along with LaAlO3 as a minor phase at 1400 °C. However, the concentration of LaAlO3 phase increased with increase in the sintering temperature and it became a major phase at 1475 °C. Maximum density was obtained for the composition with x = 0 (i.e., Sr0.6Ca0.4LaAlO4 ceramics) sintered at 1450 °C for 4 h. The TiO2 addition lowered the maximum densification temperature to 1400 °C from 1450 °C. The microwave dielectric properties varied linearly with increasing the volume fraction of TiO2 (x value). Relative permittivity (εr) increased from 20.7 to 31.1, Qufo decreased from 95,250 to 65,000 GHz, and τf was tuned through zero and increased from − 29.5 to + 25.4 ppm/°C with increase in the x value from 0 to 0.2. In the present study, εr ≈ 24.8, Qufo ≈ 83,500 GHz, and a near-zero τf ≈ − 2.5 ppm/°C was obtained for the composition with 10wt% addition of TiO2. [ABSTRACT FROM AUTHOR]

Mg0.95Ni0.05Ti0.98Zr0.02O3 and CaTiO3 were prepared separately using solid state reaction method. The effect of CaTiO3 addition on the microwave dielectric properties of Mg0.95Ni0.05Ti0.98Zr0.02O3 was investigated to get low loss and temperature stable ceramics in (1 – x)Mg0.95Ni0.05Ti0.98Zr0.02O3-xCaTiO3 series. Mg0.95Ni0.05Ti0.98Zr0.02O3 formed as the major phase along with Mg0.95Ni0.05Ti2O5 phase that formed as minor secondary phase for the composition with x = 0. Microwave dielectric properties ∈r ~ 17.1, Qufo of 195,855 GHz and τf of –46.3 ppm/°C were obtained for the composition with x = 0. The positive τf value of CaTiO3, tuned the τf value of Mg0.95Ni0.05Ti0.98Zr0.02O3 through zero and ∈r ~ 28.4, Qufo ~ 108,775 GHz and τf ~ 3.1 ppm/°C were attained for x = 0.15 in this study. This composition is the best choice for high frequency applications. [ABSTRACT FROM AUTHOR]

The ceramics in Sr5−xBixTi1+xNb4−xO17 (x = 4, 3) series were prepared using solid state sintering method. The phase and microwave dielectric properties were investigated. The parent phase Sr2Bi3Ti4NbO17 and SrBi4Ti5O17 phases did not formed along the Sr5−xBixTi1+xNb4−xO17 series for the compositions with x = 3 and 4. The SrBi4Ti4O15 phase formed as the major phase along with some secondary Bi2Ti2O7 and SrTiO3 phases for the composition with x = 4 in Sr5−xBixTi1+xNb4−xO17 series. For the composition with x = 3 in Sr5−xBixTi1+xNb4−xO17 series, Nb based Bi2Ti2O7 pyrochlore phase formed as the major phase along with SrBi3Ti2NbO12 phase as a secondary phase. In this study, good combination of microwaves dielectric properties i.e., εr ~ 166, Qufo 8888 GHz and τf ~ 3.4 ppm/°C is obtained for the compositions with x = 4 sintered at 1200 °C and εr ~ 88, Qufo~ 12,500 GHz and τf ~ − 9.36 ppm/°C is obtained for the composition with x = 3 sintered at 1200 °C. [ABSTRACT FROM AUTHOR]

In this study the synthesis of bi-phase nanoparticles of Fe1.46Zn0.5La0.04Cu0.5O4 (FZLCs) ceramics were first carried out by Sol-gel method and then nanocomposites of FZLCs with polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and polyethylene oxide (PEO) were prepared by one-pot blending technique. XRD, FT-IR, TG/DTA and SEM techniques were applied for complete characterization of composites. Rheological and dielectric properties of all nanocomposites were studied in detail for their comparative performance. TGA results reveal the highly thermal stability for all nanocomposites in this order i.e. FLZCs/PEO > FLZCs/PVA > FZLCs/PVP > FZLCs/PEG. Rheological properties show that these materials are rigid, pseudo plastic and non-Newtonian in nature. The increase in values for storage modulus (G′) and loss modulus (G′′) with increasing angular frequency owed to the shear thinning behavior of these nanocomposites. Dielectric properties show good agreement to that of energy storage substances which means that these materials have potential to be applied in storage devices. [ABSTRACT FROM AUTHOR]

Solid-state sintering method was used for the synthesis of Mg1−xCoxSiO3 (x = 0–0.25) ceramics. Phase, microstructure and microwave dielectric properties of the ceramics were investigated. With increase in Co2+ content, the increase was observed in the lattice parameters. The Qufo value of MgSiO3 was enhanced from 103,453 to 145,846 GHz with increasing the value of x content from 0 to 0.15. The Co2+ substitution also led to an obvious decrease in the sintering temperature by ~ 100 °C. Clino-enstatite phase formed for the composition with x = 0 while Proto-enstatite formed as the major along with minor clino-enstatite phase for the compositions with x > 0. Good dielectric properties at microwave frequencies i.e. εr ~ 8.11, Qufo ~ 145,846 GHz and τf ~ − 12 ppm/°C were obtained for the composition with x = 0.15 sintered at 1350 °C for 9 h. This is suggested to be a very favorable dielectric material for millimeterwave applications. [ABSTRACT FROM AUTHOR]

The compositions in Sr2Ca3Ta4Ti1−xZrxO17 (0 ≤ x ≤ 0.12) series were designed and fabricated by solid state sintering method. All the compositions formed single phases and crystallized in an orthorhombic crystal structure. Zr substitution led to the enhancing of the microwave dielectric properties by tuning the τf value through zero and increased the Qufo value from 12,540 to 14,970 GHz with a slight decrease in εr. In the present study, a good combination of εr ~ 51, Qufo ~ 145,43 GHz and τf ~ 3 ppm/°C were obtained for Sr2Ca3Ta4Ti0.90Zr0.1O17 ceramic sintered at 1575 °C for 4 h. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (ɛr) 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, ɛr = 45.5 and Q ufo = 7919 GHz, correspond to the SrLa4Ti5-xSnxO17 composition with x = 1. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]