Trends In Temperature Dependence Research Articles

Temperature effects on growth rates and fatty acid content in freshwater algae and cyanobacteria

Mass cultivation of algae for biofuel and other bioproduct production in outdoor, open raceway ponds has some considerable economic advantages. However, these systems would be subject to fluctuations in temperature (among other environmental factors), which can have dramatic effects on the growth rates of algal species and impact the overall productivity and quality of targeted algal crops. This study sought to elucidate the effects of temperature on algal growth rates, biomass accumulation, fatty acid production and composition. We surveyed 26 algal species from 5 different functional groups, growing them at 6 different temperatures between 9 and 32 °C. For each surveyed species, we collected eco-physiological trait data including maximum growth rate, thermal optimum (Topt), thermal niche width, and lower and upper temperature limits for growth (CTmin and CTmax, respectively); these data were also pooled for analysis at the functional group level. Responses to temperature varied among species, but at the functional group level we determined that the cyanobacteria have the highest thermal optimum (30.6 ± 2.3 °C), followed by chlorophytes (25.7 ± 0.1 °C) and diatoms (24.0 ± 0.4 °C). Temperature-specific fatty acid (FA) production was mostly controlled by growth rates, though some change in production was attributable to modification of intracellular FA stores. Temperature affected FA profiles in diverse ways, with no consistent trends across species or functional groups. In sum, temperature significantly impacts the overall productivity of algal biofuel systems by influencing species growth rates and fatty acid production. While algal growth rates varied predictably with temperature, we did not find the generalizable trends in temperature dependence of FA composition, suggesting that some aspects of algal cultivation for bioproducts in outdoor, open-air systems may be less predictable. However, a compilation of algal growth and FA composition responses to temperature, such as ours, may be useful for choosing appropriate species for given temperature regimes.

NIR reflectance spectroscopy of hydrated and anhydrous sodium carbonates at different temperatures

Recent space-based observations have revealed or suggested the existence of various types of carbonate salts in several Solar System bodies, such as Mars, Ceres, Enceladus, and Europa. Natrite is the main component of the crater Occator's faculae observed in detail by the Dawn spacecraft on the dwarf planet Ceres. Sodium carbonates are thought to form as precipitates in brines, originating in aqueous environments in the subsurface of Ceres and icy bodies. Here we report about near-infrared (0.8–4.2 μm) reflectance spectroscopic investigations on three compounds, namely natrite (anhydrous Na2CO3), monohydrated sodium carbonate (Na2CO3•H2O, thermonatrite) and decahydrate sodium carbonate (Na2CO3•10H2O, natron). Spectral measurements have been carried out in the overall temperature range 93–279 K, representative of planetary surfaces. The analysis of diagnostic spectral signatures shows different temperature-dependent trends for several band parameters, as well as different behavior as a function of the grain size for a given temperature. While spectra of natrite are characterized by several CO3 absorptions, broad and strong absorption features due to H2O dominate the spectra of heavily hydrated natron. The intermediate sample (monohydrated) shows multiple bands due to the overlap of CO3 and H2O vibrational modes. Our temperature-dependent laboratory spectra are compared with Dawn-VIR spectra of Ceres and with Galileo-NIMS spectra of Europa.

Polluted white dwarfs: constraints on the origin and geology of exoplanetary material

White dwarfs that have accreted rocky planetary bodies provide unique insights regarding the bulk composition of exoplanetary material. The analysis presented here uses observed white dwarf atmospheric abundances to constrain both where in the planetary system the pollutant bodies originated, and the geological and collisional history of the pollutant bodies. At least one, but possibly up to nine, of the 17 systems analysed have accreted a body dominated by either core-like or mantle-like material. The approximately even spread in the core mass fraction of the pollutants and the lack of crust-rich pollutants in the 17 systems studied here suggest that the pollutants are often the fragments produced by the collision of larger differentiated bodies. The compositions of many pollutants exhibit trends related to elemental volatility, which we link to the temperatures and, thus, the locations at which these bodies formed. Our analysis found that the abundances observed in 11 of the 17 systems considered are consistent with the compositions of nearby stars in combination with a trend related to elemental volatility. The even spread and large range in the predicted formation location of the pollutants suggests that pollutants arrive in white dwarf atmospheres with a roughly equal efficiency from a wide range of radial locations. Ratios of elements with different condensation temperatures such as Ca/Mg, Na/Mg, and O/Mg distinguish between different formation temperatures, whilst pairs of ratios of siderophilic and lithophilic elements such as Fe/Mg, Ni/Mg and Al/Mg, Ca/Mg distinguish between temperature dependent trends and geological trends.

Effects of High Temperature and Thermal Cycling on the Performance of Perovskite Solar Cells: Acceleration of Charge Recombination and Deterioration of Charge Extraction.

In this work, we investigated the effects of high operating temperature and thermal cycling on the photovoltaic (PV) performance of perovskite solar cells (PSCs) with a typical mesostructured (m)-TiO2-CH3NH3PbI3-xClx-spiro-OMeTAD architecture. After temperature-dependent grazing-incidence wide-angle X-ray scattering, in situ X-ray diffraction, and optical absorption experiments were carried out, the thermal durability of PSCs was tested by subjecting the devices to repetitive heating to 70 °C and cooling to room temperature (20 °C). An unexpected regenerative effect was observed after the first thermal cycle; the average power conversion efficiency (PCE) increased by approximately 10% in reference to the as-prepared device. This increase of PCE was attributed to the heating-induced improvement of the crystallinity and p doping in the hole transporter, spiro-OMeTAD, which promotes the efficient extraction of photogenerated carriers. However, further thermal cycles produced a detrimental effect on the PV performance of PSCs, with the short-circuit current and fill factor degrading faster than the open-circuit voltage. Similarly, the PV performance of PSCs degraded at high operation temperatures; both the short-circuit current and open-circuit voltage decreased with increasing temperature, but the temperature-dependent trend of the fill factor was the opposite. Our impedance spectroscopy analysis revealed a monotonous increase of the charge-transfer resistance and a concurrent decrease of the charge-recombination resistance with increasing temperature, indicating a high recombination of charge carriers. Our results revealed that both thermal cycling and high temperatures produce irreversible detrimental effects on the PSC performance because of the deteriorated interfacial photocarrier extraction. The present findings suggest that the development of robust charge transporters and proper interface engineering are critical for the deployment of perovskite PVs in harsh thermal environments.

Dynamics of ion-molecule reactions of SO2.+ with H2O and CH4

SynopsisThe reaction dynamics and the temperature-dependent kinetic trend of the SO2.+ ion-molecule reactions with water and methane have been studied using the tunable synchrotron radiation to produce excited SO2.+ ions and ab-initio methods. The experimental results show that only one product, HSO2+, is formed in both reactions and its yield displays different trends with the photon energy. DFT and VTST calculations have been used to explore the dynamics of the reactions and to calculate the rate constants at different temperatures.

Formation of multiferroic PbTiO3/PbFe12O19 composite by exceeding the solubility limit of Fe in PbTiO3

PbTiO3/PbFe12O19 composites have been synthesized by keeping the Fe concentration (x) in PbFexTi1−xO3 beyond solubility limit, i.e., x> 0.1% and 5% Pb excess. Both these factors have been successfully utilized to extract Fe doped PbTiO3 tetragonal phase which is composited with Magnetoplumbite (PbFe12O19) phase. A systematic evolution of the tetragonality of the former and improved stoichiometry of the later constituent has been observed. As x increases, emergence of additional Raman mode around 650cm−1 with Fe addition was observed. Systematic increase in the relative intensity of this mode with x, showed that this mode corresponds to the magnetoplumbite phase. In addition to that resultant composite exhibited noticeable systematic decrease in the value of the energy gap as a function of x. Increasing Fe concentration in PbTiO3 constituent, led to monotonic decrease in c/a and increase in strain experienced by PbTiO3. Increase in the value of the saturation polarization was observed up to x = 0.4, which is identified to be associated with the strain induced by the dopant. A comprehensive magnetic characterization revealed monotonic decrease in magnetization with temperature for all compositions. Finally, we found an anomalous temperature dependent trend in the magnetic coercivity which is explained in terms of low temperature decrease in effective magnetic anisotropy by including magneto-electric coupling. Both constituent phases in the composite being ferroelectric and ferromagnetic at room temperature led to formation of better multiferroic properties and exhibited tunable physical properties with x.

Quantification of different contributions to dissipation in elastomer nanoparticle composites

We present an approach to quantify different contributions to dissipation in elastomer nanoparticle composites based on strain sweeps. A modified Kraus equation is successfully used to approximate the loss modulus depending on strain amplitude G″γ measured at different temperatures. For natural rubber composites containing >10 vol% carbon black or >3 vol% carbon nanotubes two different contributions to dissipation due to (i) breaking and (ii) deformation of glassy rubber bridges in the filler network are identified. Filler fraction and temperature-dependent trends support physical pictures considering that glassy rubber bridges are responsible for the visco-elasticity of the filler network. Constant extra contributions to dissipation are associated with the bulk-like fraction of the elastomer matrix or filler network independent effects. The achieved understanding should be very important for the optimization of elastomer nanoparticle composites for special applications like tire treads.

Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene.

Location recognition at the molecular scale provides valuable information about the nature of functional molecular materials. This study presents a novel location sensing approach based on an endohedral metallofullerene, Ce@C82, using its anisotropic magnetic properties, which lead to temperature-dependent paramagnetic shifts in (1)H NMR spectra. Five site-isomers of Ce@C82CH2-3,5-C6H3Me2 were synthesized to demonstrate the spatial sensing ability of Ce@C82. Single-crystal structures, absorption spectra, and density functional theory calculations were used to select the plausible addition positions in the radical coupling reaction, which preferentially happens on the carbon atoms with high electron density of the singly occupied molecular orbital (SOMO) and positive charge. Temperature-dependent NMR measurements demonstrated unique paramagnetic shifts of the (1)H peaks, which were derived from the anisotropic magnetism of the f-electron in the Ce atom of the isomers. It was found that the magnetic anisotropy axes can be easily predicted by theoretical calculations using the Gaussian 09 package. Further analysis revealed that the temperature-dependent trend in the shifts is clearly predictable from the distance and relative position of the proton from the Ce atom. Hence, the Ce-encapsulated metallofullerene Ce@C82 can provide spatial location information about nearby atoms through the temperature-dependent paramagnetic shifts of its NMR signals. It can act as a molecular probe for location sensing by utilizing the anisotropic magnetism of the encapsulated Ce atom. The potentially low toxicity and stability of the endohedral fullerene would make Ce@C82 suitable for applications in biology and material science.

Exploration of the mechanisms of temperature-dependent grain boundary mobility: search for the common origin of ultrafast grain boundary motion

The temperature dependence of grain boundary mobility is complex, varied, and rarely fits ideal Arrhenius behavior. This work presents a series of case studies of planar grain boundaries in a model FCC system that were previously demonstrated to exhibit a variety of temperature-dependent mobility behaviors. It is demonstrated that characterization of the mobility versus temperature plots is not sufficient to predict the atomic motion mechanism of the grain boundaries. Herein, the temperature-dependent motion and atomistic motion mechanisms of planar grain boundaries are driven by a synthetic, orientation-dependent, driving force. The systems studied include CSL boundaries with $$\Sigma $$ values of 5, 7, and 15, including both symmetric and asymmetric boundaries. These boundaries represent a range of temperature-dependent trends including thermally activated, antithermal, and roughening behaviors. Examining the atomic-level motion mechanisms of the thermally activated boundaries reveals that each involves a complex shuffle, and at least one atom that changes the plane it resides on. The motion mechanism of the antithermal boundary is qualitatively different and involves an in-plane coordinated shuffle that rotates atoms about a fixed atom lying on a point in the coincident site lattice. This provides a mechanistic reason for the observed high mobility, even at low temperatures, which is due to the low activation energy needed for such motion. However, it will be demonstrated that this mechanism is not universal, or even common, to other boundaries exhibiting non-thermally activated motion. This work concludes that no single atomic motion mechanism is sufficient to explain the existence of non-thermally activated boundary motion.

Length-dependent thermal transport in one-dimensional self-assembly of planar π-conjugated molecules.

This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become 'amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the 'amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport.

Orientation epitaxy of Ge1−xSnxfilms grown on single crystal CaF2substrates

Ge1−xSnx films were grown via physical vapor deposition below the crystallization temperature of Ge on single crystal (111) and (100) CaF2 substrates to assess the role of Sn alloying in Ge crystallization. By studying samples grown at several growth temperatures ranging from 250 °C to 400 °C we report temperature-dependent trends in several of the films' properties. X-ray diffraction theta vs. two-theta (θ/2θ) scans indicate single orientation Ge1−xSnx(111) films are grown on CaF2(111) substrates at each temperature, while a temperature-dependent superposition of (111) and (100) orientations are exhibited in films grown on CaF2(100) above 250 °C. This is the first report of (111) oriented Ge1−xSnx grown on a (100) oriented CaF2 substrate, which is successfully predicted by a superlattice area matching model. These results are confirmed by X-ray diffraction pole figure analysis. θ/2θ results indicate substitutional Sn alloying in each film of about 5%, corroborated by energy dispersive spectroscopy. Additionally, morphological and electrical properties are measured by scanning electron microscopy, atomic force microscopy and Hall mobility measurements and are also shown to be dependent upon growth temperature.

Nitrogen Incorporation during Seeded Sublimation Growth of 4H-SiC and 6H-SiC

We address the problem of nitrogen incorporation during bulk crystal growth of 4H-SiC and 6H-SiC by seeded sublimation method. The partial pressure of nitrogen and temperature dependence were considered in bulk SiC crystals. Free carrier concentration and incorporated nitrogen were determined using Raman spectroscopy and Secondary Ion Mass Spectrometry, respectively. The incorporated nitrogen at the (000-1) C-face of 4H-SiC and 6H-SiC is found to be independent of the polytype of the crystal. Higher desorption rate at Si-face compared to C-face is found, using a Langmuir equation, which is attributed to the difference in bond density between the two polar faces. The increased nitrogen desorption when growth temperature increases is believed to be the most contributing factor, based on the temperature dependent trends.

ACCURATE GRAVITIES OF F, G, AND K STARS FROM HIGH RESOLUTION SPECTRA WITHOUT EXTERNAL CONSTRAINTS

We demonstrate a new procedure to derive accurate and precise surface gravities from high resolution spectra without the use of external constraints. Our analysis utilizes Spectroscopy Made Easy (SME) with robust spectral line constraints and uses an iterative process to mitigate degeneracies in the fitting process. We adopt an updated radiative transfer code, a new treatment for neutral perturber broadening, a line list with multiple gravity constraints and separate fitting for global stellar properties and abundance determinations. To investigate the sources of temperature dependent trends in determining log g noted in previous studies, we obtained Keck HIRES spectra of 42 Kepler asteroseismic stars. In comparison to asteroseismically determined log g our spectroscopic analysis has a constant offset of 0.01 dex with a root mean square (RMS) scatter of 0.05 dex. We also analyzed 30 spectra which had published surface gravities determined using the $a/R_*$ technique from planetary transits and found a constant offset of 0.06 dex and RMS scatter of 0.07 dex. The two samples covered effective temperatures between 5000K and 6700K with log g between 3.7 and 4.6.

Temperature dependence of a refractive index sensor based on a macrobending micro-plastic optical fiber.

We investigate the temperature dependence of a refractive index (RI) sensor based on a macrobending micro-plastic optical fiber (m-POF) both theoretically and experimentally. The performance of the RI sensor at different temperatures (10°C-70°C) is measured and simulated over an RI range from 1.33 to 1.45. It is found that the temperature dependent bending loss and RI measurement deviation monotonically change with temperature, and the RI deviation has a higher gradient with temperature variation for a higher measured RI. Because of the linear trend of temperature dependence of the sensor, it is feasible to correct for changes in ambient temperature.

Characterization of high temperature tensile and creep–fatigue properties of Alloy 800H for intermediate heat exchanger components of (V)HTRs

Alloy 800H is considered as a candidate material for intermediate heat exchanger (IHX) components of (very) high temperature reactors (V)HTRs. Qualification of the this alloy for the aforementioned nuclear applications requires understanding of its high temperature tensile, low-cycle fatigue behavior and creep–fatigue interactions because the IHX components suffer from combined creep–fatigue loadings resulting from thermally induced strain cycles associated with start-up and shutdown cycles. To this end, in this paper, the tensile properties of the Alloy 800H base and tungsten inert gas (TIG) welded materials are studied at three different temperatures, room temperature 21, 700 and 800°C. Low cycle fatigue (LCF) behavior of the base material is investigated at 800°C with no-hold time (no-HT) and hold time (HT) to study creep–fatigue interactions. The tensile test results showed substantial differences between the strength and ductility properties of the base and weld materials at all 3 temperatures, however, the trends in temperature dependence of tensile properties are similar for both base and weld materials. LCF studies with no-HT and HT showed a strong influence of HT on the low cycle fatigue life of this alloy illustrating the substantial influence of creep mechanisms at 800°C. Finally, cumulative values of creep versus fatigue damage fractions are plotted in a creep–fatigue interaction diagram and these results are discussed with respect to the existing bi-linear damage summation curve for Alloy 800H in ASME Code Case N-47 in order to understand the synergetic effects of both the damage mechanisms.

The effect of water temperature on air entrainment, bubble plumes, and surface foam in a laboratory breaking-wave analog

Air-entraining breaking waves form oceanic whitecaps and play a key role in climate regulation through air-sea bubble-mediated gas transfer, and sea spray aerosol production. The effect of varying sea surface temperature on air entrainment, subsurface bubble plume dynamics, and surface foam evolution intrinsic to oceanic whitecaps has not been well studied. By using a breaking wave analog in the laboratory over a range of water temperatures (Tw = 5°C to Tw = 30°C) and different source waters, we have examined changes in air entrainment, subsurface bubble plumes, and surface foam evolution over the course of a breaking event. For filtered seawater, air entrainment was estimated to increase by 6% between Tw = 6°C and Tw = 30°C, driven by increases of about 43% in the measured surface roughness of the plunging water sheet. After active air entrainment, the rate of loss of air through bubble degassing was more rapid at colder water temperatures within the first 0.5 s of plume evolution. Thereafter, the trend reversed and bubbles degassed more quickly in warmer water. The largest observed temperature-dependent differences in subsurface bubble distributions occurred at radii greater than about 700 μm. Temperature-dependent trends observed in the subsurface bubble plume were mirrored in the temporal evolution of the surface whitecap foam area demonstrating the intrinsic link between surface whitecap foam and the subsurface bubble plume. Differences in foam and plume characteristics due to different water sources were greater than the temperature dependencies for the filtered seawater examined.

Temperature-dependent efficiency droop of blue InGaN micro-light emitting diodes

Temperature-dependent trends in radiative and Auger recombination coefficients have been determined at different injection carrier concentrations using InGaN micro-light emitting diodes 40 μm in diameter. The differential lifetime was obtained first from the measured modulation bandwidth and was then employed to calculate the carrier concentration in the quantum well active region. When the temperature increases, the carrier concentration increases, but both the radiative and Auger recombination coefficients decrease. In addition, the temperature dependence of radiative and Auger recombination coefficients is weaker at a higher injection carrier concentration, which is strongly related to phase space filling.

Formation of ionic complexes in cryogenic matrices: A case study using co-deposition of Cu− with rare gas cations in solid argon

Matrix isolation spectra have been obtained for ionic species formed from a beam of mass-selected ions, with a coincident beam of externally generated counter-ions used to provide charge balance. Infrared spectra were obtained for copper carbonyl complexes formed following deposition of Cu(-) ions with rare-gas counter-cations into CO-doped argon matrices. Both anionic and neutral copper carbonyl complexes Cu(CO)(n)(q) (n = 1-3; q = 0, -1) were observed in the spectra, with peak positions corresponding to previously reported assignments; new partially resolved bands appearing in the range 1830-1845 cm(-1) are assigned to larger [Cu(CO)3●(CO)n](-) aggregates, having additional CO ligands in the second solvation shell. The experimental geometry ensures that all Cu-centers initially arrive at the matrix as anions, so the relative abundance of anionic relative to neutral complexes is much higher than in previous studies employing alternative methods for ion deposition; this allows for monitoring of electron-transfer processes between anions and cations in the matrix. Comparison of time-dependent vs. temperature-dependent trends reveals that there are two distinct mechanisms by which the population of anionic complexes is converted into neutral complexes: short-range electron transfer between a cation-anion pair following diffusion, and long-range electron transfer involving photodetachment of an electron from the anion into the conduction band of solid argon, resulting in eventual recombination of the electron with a cation in a remote matrix site. The spectra also show a marked dependence on the deposition temperature and dopant concentration, in that 100-fold higher CO concentrations were required during deposition with the sample window at 10 K compared to that used at 20 K, in order to obtain a similar distribution of copper carbonyl complexes. Furthermore, although no carbonyl complexes are observed initially when low concentrations of CO are used at 10 K, upon warming the matrix to 15 K, the neutral di- and tricarbonyl peaks appear abruptly, which is attributed to fast diffusion of CO stimulated by the energy released upon short-range electron-transfer between Cu(-):counter-cation pairs.

Dielectric and infrared properties of SrTiO3 single crystal doped by 3d (V, Mn, Fe, Ni) and 4f (Nd, Sm, Er) ions

In this study, the effects of doping by 3d (V, Mn, Fe, Ni) and 4f (Nd, Sm, Er) ions on dielectric and infrared properties of SrTiO3 (STO) single crystals are investigated. It is well known that doping of the SrTiO3 can change the dielectric properties of the STO from an insulator to an n-type semiconductor, and even to a metallic conductor. Dielectric and infrared (IR) properties of the undoped STO and doped STO single crystals are analyzed using dielectric spectroscopy (80 kHz-5 MHz), transmission (200 cm−1–4000 cm−1), and reflection spectroscopy (50 cm−1–2000 cm−1). It is found that doping by the 3d ions reduces the value of dielectric permittivity, but the trend of temperature dependence of the dielectric permittivity remains almost unchanged. On the other hand, dielectric spectroscopy measurements for samples doped by 4f ions show the anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition. There are two fractures of temperature dependences of inverse dielectric permittivity εr−1(T). Transmittance spectroscopy measurements show that there are differences in the shape of the spectrum in the mid-IR region between the undoped STO and the one doped by 4f ions. The differences in the reflectance spectrum between the STO:Nd and STO are analyzed in detail.

Modifications in the frustrated magnetism, oxidation state of Co and magnetoelectric coupling effects induced by a partial replacement of Ca by Gd in the spin-chain compound Ca3Co2O6

We have systematically investigated the influence of the gradual replacement of Ca by Gd on the magnetic and complex dielectric properties of the well-known geometrically frustrated spin-chain system Ca3Co2O6 (TN = 24 K with additional magnetic transitions below 12 K), by studying the series Ca3−xGdxCo2O6 (x ≤ 0.7), down to 1.8 K. Heat-capacity measurements establish that the reduction of TN with Gd substitution is much less compared to that by Y substitution. The magnetic moment data reveal that there are changes in the oxidation state of Co as well, unlike for Y substitution, beyond x = 0.2. Thus, despite being isovalent, both these substitutions interestingly differ in changing these magnetic properties in these oxides. We propose that the valence electrons of Y and those of R ions play different roles in deciding the magnetic characteristics of these mixed oxides. It is observed that a small amount (x = 0.3) of Gd substitution for Ca is enough to suppress glassy ac magnetic susceptibility behavior for the peak around 12 K. An additional low-temperature magnetic anomaly close to 5 K gets more prominent with increasing Gd concentration as revealed by heat-capacity data. Trends in temperature dependence of complex dielectric behavior were also tracked with varying composition and a frequency dependence is observed, not only for the transition in the region around 10 K (for some compositions), but also for the 5 K transition which is well resolved for a higher concentration of Gd. Thus, the Gd-substituted Ca3Co2O6 series is shown to reveal interesting magnetic and dielectric behaviors of this family of oxides.