Ca
Cd
Cu
Ti
O
F
(
=
= 0, 0.10, and 0.15) ceramics were successfully prepared
a conventional solid-state reaction (SSR) method. A single-phase CaCu
Ti
O
with a unit cell ∼7.393 Å was detected in all ...of the studied ceramic samples. The grain sizes of sintered Ca
Cd
Cu
Ti
O
F
ceramics were significantly enlarged with increasing dopant levels. Liquid-phase sintering mechanisms could be well matched to explain the enlarged grain size in the doped ceramics. Interestingly, preserved high dielectric permittivities, ∼36 279-38 947, and significantly reduced loss tangents, ∼0.024-0.033, were achieved in CdF
codoped CCTO ceramics. Density functional theory results disclosed that the Cu site is the most preferable location for the Cd dopant. Moreover, F atoms preferentially remained close to the Cd atoms in this structure. An enhanced grain boundary response might be a primary cause of the improved dielectric properties in Ca
Cd
Cu
Ti
O
F
ceramics. The internal barrier layer capacitor model could well describe the colossal dielectric response of all studied sintered ceramics.
We studied five alkaline earth dicarbide systems MAEC2 (where M-AE = Be-Ba) by using ab initio random structure search. For BeC2 and MgC2, the lowest energy and dynamically stable configuration ...consists of five-membered carbon rings connected to each other via an individual carbon atom, stabilized through the donation of electrons from the surrounding alkaline earth ions. For CaC2, SrC2, and BaC2, our study shows that the chain crystal structure is more stable than the predicted structure due to strains induced by the increasing size of alkaline earth metal ions. The reaction energies of the typical synthesis pathway are comparable to those calculated for the experimental reaction of the known chain-type structure. Finally, the proposed structure should be optically distinguishable due to a significantly narrower band gap.
The effects of the sintering temperature on microstructures, electrical properties, and dielectric response of 1%Cr
/Ta
co-doped TiO
(CrTTO) ceramics prepared using a solid-state reaction method were ...studied. The mean grain size increased with an increasing sintering temperature range of 1300-1500 °C. The dielectric permittivity of CrTTO ceramics sintered at 1300 °C was very low (ε' ∼198). Interestingly, a low loss tangent (tanδ ∼0.03-0.06) and high ε' (∼1.61-1.9 × 10
) with a temperature coefficient less than ≤ ±15% in a temperature range of -60 to 150 °C were obtained. The results demonstrated a higher performance property of the acceptor Cr
/donor Ta
co-doped TiO
ceramics compared to the Ta
-doped TiO
and Cr
-doped TiO
ceramics. According to a first-principles study, high-performance giant dielectric properties (HPDPs) did not originate from electron-pinned defect dipoles. By impedance spectroscopy (IS), it was suggested that the giant dielectric response was induced by interfacial polarization at the internal interfaces rather than by the formation of complex defect dipoles. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of Ti
, resulting in the formation of semiconducting parts in the bulk ceramics. Low tanδ and excellent temperature stability were due to the high resistance of the insulating layers with a very high potential barrier of ∼2.0 eV.
CsSn
1−x
Pb
x
I
3
films were prepared from mixed CsI, SnI
2
and/or PbI
2
solutions at five different Pb/Sn ratios (x = 0, 0.2, 0.5, 0.8 and 1) at room temperature. The color of the CsSn
1−x
Pb
x
I
3
...films varied with their Pb/Sn ratios. At a Pb/Sn ratio of 0.5, CsSn
0.5
Pb
0.5
I
3
had the darkest color, whereas films at other Pb/Sn ratios displayed dark brown or yellowish colors. The XRD spectra of the as-prepared CsSn
1−x
Pb
x
I
3
films matched the δ-phase (yellow-phase) nonperovskite structure quite well. Solid-state dye-sensitized solar cells (S-DSSCs) were assembled by directly dropping the mixed CsI, SnI
2
and/or PbI
2
solution onto TiO
2
-coated-dye electrodes and drying them at room temperature. A CsSn
0.5
Pb
0.5
I
3
based S-DSSC generated the highest efficiency (3.47%) of the five conditions (CsSn
1−x
Pb
x
I
3
, x = 0, 0.2, 0.5, 0.8 and 1). This is attributed to the dark color and good continuity of the CsSn
0.5
Pb
0.5
I
3
film, its high shunt-resistance (10,377.10 Ω) and high incident-photon collecting efficiency of CsSn
0.5
Pb
0.5
I
3
based S-DSSCs.
The aim of this work was to investigate the effect of free oxygen radicals and free electrons in a Ca
Al
O
(C12A7) cement structure on the optical, electronic and antibacterial activity of this ...material. Ca
Al
O
was successfully fabricated via rapid heating to high temperatures by high frequency electromagnetic induction. Ca
Al
O
cement samples were characterized using XRD and UV-Vis-DRS spectroscopy. The morphology and chemical composition of the samples were also investigated using SEM and EDS techniques. The presence of free oxygen radicals (O
ions) in the insulating structure of Ca
Al
O
was confirmed using Raman spectroscopy showing a spectrum peak at 1067 cm
. The excitation of free electrons in the Ca
Al
O
cement was indicated by UV-Vis absorption spectra at 2.8 eV and an optical energy gap of 3.5 eV, which is consistent with the first-principles calculations for the band energy level. The effects of free oxygen radicals and free electrons in the Ca
Al
O
structure as antibacterial agents against
.
and
.
were investigated using an agar disk-diffusion method. The presence of O
anions as a reactive oxygen species (ROS) at the surface of Ca
Al
O
caused inhibition of
.
and
.
cells. The free electrons in the conducting C12A7 reacted with O
gas to produce ROS, specifically super oxides (O
), superoxide radicals (O
), hydroxyl radicals (OH
) and hydrogen peroxide (H
O
), which exhibited antibacterial properties. Both mechanisms were active against bacteria without effects from nano-particle sized materials and photocatalytic activity. The experimental results showed that the production of ROS from free electrons was greater than that of the free O
anions in the structure of Ca
Al
O
. The antibacterial actions for insulating and conducting Ca
Al
O
were different for
.
and
.
. Thus, Ca
Al
O
cement has antibacterial properties that do not require the presence of nano-particle sizes materials or photocatalysis.
Cost-effective reduced graphene oxide sheets decorated with magnetite (Fe
O
) nanoparticles (Fe
O
-rGO) are successfully fabricated via a chemical vapor deposition (CVD) technique using iron (III) ...nitrate as an iron precursor, with glucose and CH
as carbon sources, and NaCl as a supporting material. TEM analysis and Raman spectroscopy reveal hierarchical nanostructures of reduced graphene oxide (rGO) decorated with Fe
O
nanoparticles. Fe K-edge x-ray absorption near edge structure (XANES) spectra confirm that the nanoparticles are Fe
O
with a slight shift of the pre-edge peak position toward higher energy suggesting that the fabricated Fe
O
nanoparticles have a higher average oxidation state than that of a standard Fe
O
compound. The hierarchical Fe
O
-rGO is found to exhibit an excellent catalytic activity toward the reduction of triiodide to iodide in a dye-sensitized solar cell (DSSC) and can deliver a solar cell efficiency of 6.65%, which is superior to a Pt-based DSSC (6.37%).
Delafossite CuFe sub(1-x)Ge sub(x)O sub(2) (0.0 < or = x < or = 0.1) semiconductors were synthesized by solid-state reaction. The effects of Ge concentration on microstructural, optical, magnetic and ...electrical properties were investigated. X-ray diffraction (XRD) analysis results reveal the delafossite structure of all the samples. The lattice spacing of CuFe sub(1-x)Ge sub(x)O sub(2) decreased with increasing substitution of Ge at the Fe site. The optical properties measured at room temperature by UV-visible spectroscopy showed an absorption peak at 283 nm (4.38 eV). The corresponding direct optical band gap was found to decrease with increasing Ge content (from 3.69 eV for x = 0 to 3.61 eV for x = 0.10), exhibiting transparency in the visible region. The magnetic hysteresis loops measured at room temperature showed that the Ge-doped CuFeO sub(2) samples exhibit ferromagnetic behavior. The Curie temperature suggests that ferromagnetism originates from CuFe sub(1-x)Ge sub(x)O sub(2) matrices. The substitution of Fe super(3+) by Ge super(4+) produces a mixed effect on the magnetic properties of CuFeO sub(2) delafossite oxide. The resistivity of CuFe sub(0.99)Ge sub(0.01)O sub(2) was observed to be ~0.1 Omega times cm at room temperature.
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