Multiferroic materials combine two or more ferroic orders such as ferroelectricity, ferromagnetism and ferroelasticity. They have a great interest for the development of the next generations of digital electronic memory devices. Bismuth ferrite has shown to posess both ferroelectric and magnetic order at room temperature, which makes it both scientifically and comercially interesting.The negative impact on the environment by using lead in mass-produced units has made development of lead-free piezoelectric materials for use in sensors, actuators and transducers prioritized and samarium substituted bismuth ferrite has shown to posess a piezoelectric response high enough to be considered for commercial applications. In this project work, 10mol% samarium substituted bismuth ferrite, Bi_{0.9}Sm_{0.1}FeO_{3}, powders have been synthesized using a wet-chemical method and calcined to a range of temperatures to achieve a range of nanocrystalline sizes in the powders. These powders has been investigated using X-ray diffraction (XRD), Rietveld refinement and differential scanning calorimetry (DSC). The powders have also been milled, pressed and sintered to pellets for ferroelectric and piezoelectric testing. The crystal structure was found to belong to the R3c group as for bismuth ferrite, BiFeO_{3}, but the unit cell geometry is changed slightly, and the ferroelectric polarizability is lowered in the case of samarium substitution. This fact is interesting regarding piezoelectricity by thereby increasing the ability to achieve a higher piezoelectric response. No results were achieved from ferroelectric and piezoelectric measurement due to the conductivity found in the sintered pellets were too high, probably due to secondary sillenite phases found in the material. There has been found a finite size effect of a decrease in unit cell volume and tetragonality, of which the decrease in volume is contradictory to the expectations. There is also clear finite size effects on the decrease of cooperative displacement of cations, a measure for the polarization, and for the lowering of the ferroelectric phase transition temperature. The finite size effect for the ferroelectric phase transition has not been reported before. The magnetic phase transition temperature also show a decrease as a clear finite size effect. A linear relationship between electric polarization and magnetic ordering has also been observed in this project. The results from this project contributes to the understanding of material properties of BiFeO_{3} and derived compositions by an investigation of substitution effects and finite size effects. The results presented here motivates further research on these materials.

A carbon powder containing carbon nanocones was used as an anode material in lithium ion batteries. The powder was also treated in different ways, chemically, with microwaves, and with heat. The carbon powder was tape casted onto copper before being assembled into batteries with lithium metal as the counter electrode. The batteries were characterized by measuring the capacity during cycling. X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the powders and casts. Fourier transformed infrared spectroscopy (FTIR) was done to both the carbon powder and the used anode material.The solid electrolyte interface (SEI) was characterized and found to contain components like ce{(CH2OCO2Li)2}, ce{Li2CO3}, and ce{ROCO2Li}. These are in accordance with what would be expected from results in the literature. SEM was used to find surface orientation of the basal and edge planes, and XRD was used to find the crystallinity.parThese results showed that more graphitized powders were better with emphasis on irreversible capacity. The treated carbon nanocone powders had higher capacity than the graphitized ones, but also higher irreversible capacity.

In this report, 10 at% lanthanum was introduced to the perovskite structure of bismuth ferrite at the expense of bismuth through a modified Pechini wet chemical method. Green body powders were calcined at several temperatures, and the lattice parameters for each size were found by Rietveld refinement of X-ray powder diffraction data. The parameters displayed strong size-dependent properties, and the rhombohedral distortion from the cubic structure was reduced by decreased particle size. With decreasing crystallite size, the Néel temperature decreased and the cooperative cationic displacement (s - t) showed size dependence at crystallite sizes below 30 nm. A size-dependency was also observed in the Curie temperature.

Interest in renewable energy resources has increased in recent years, and solar cells are one of the areas that have been subject to intensive research. For solar energy to develop into a competitive alternative to fossil fuels, the ratio between cost and efficiency has to be reduced. One of the reasons for low efficiency is the optical losses due to reflection and poor absorption of the red and infrared segment of the light spectrum. Applying more ideal anti-reflection structures and a back-side diffraction layer to increase the path length of light would certainly constitute steps in the right direction. Diatoms, a type of algae, are one of nature's most efficient light harvesting structures. It is suggested that their nano- and microporous silica shell (frustule) possess optical properties that make them attractive options for increasing the efficiency of solar cells. This project aimed at studying the structural and optical properties of selected diatom species and investigating the potential for efficiency enhancements in solar cells through the incorporation of diatoms. Two different species,emph{Coscinodiscus wailesii} and emph{Coscinodiscus sp.}, were investigated through the use of a scanning electron microscope. They were found to have different structures, with the frustule of emph{Coscinodiscus sp.} as having a more regular pore pattern and a more complex structure consisting of several silica layers. The emph{Coscinodiscus sp.} structure was chosen as the foundation for modelling a diffraction grating in GD-Calc, a Matlab implemented simulation software based on rigorous coupled-wave analysis. The diffraction simulations were carried out both on the grating in air and on the grating incorporated in solar cell-like setups. The simulations demonstrated that the diatom structure diffracted light efficiently to higher orders. It was also shown that the anti-reflection structure provided low levels of reflection for a given set of geometric combinations. The back-side diffraction grating reflected light with efficiencies of 0.9, however, the level of diffraction to higher orders was below 0.1. This study shows that that diatom frustule exhibits interesting diffraction grating properties which should be investigated further, both for solar cell schemes and for other applications.