NKN doped samples, (100-x)NKN-xSBN (0 ≤ x ≤ 10) were produced using the conventional mixed oxide route with 0.45 wt% Fe2O3 sintering aid (xSBNF). After 20-24 hours mixing, samples were calcined at 850°C and sintered at 1100–1140°C (± 180°C/hour) for 4 hours. By XRD 4 mol% SBN was found to be the solubility limit for single phase structure. By SEM, second phases were visible when 2 ≤ x ≤ 4; their structure was subsequently shown to be tungsten bronze type (TBT). 2-4 SBNF samples were high density, over 96% theoretical. For x = 0, TC = 457°C, TO-T = 234°C, Pr = 22 μC/cm2 and EC = 16.5 kV/cm. TC was found to decrease by 14.7°C and TO-T by 9.0°C per 1 mol% addition SBN. 2SBNF was the optimal formulation in terms of microstructure and electrical properties, with average grain size 3 μm, Pr = 25 μC/cm2 and EC = 8.8 kV/cm, ρ = 4.7 kΩm and Q = 1.16 eV. This material comprised approximately 90% orthorhombic and 10% tetragonal phases coexisting. Pseudo-cubic lattice parameters are a’ = c’ = 3.947180 Å, and b’ = 3.999996 Å for orthorhombic phase; the tetragonal has a’ = c’ = 3.989798 Å, and b’ = 3.975777 Å.Synchrotron XRD studies were undertaken as a function of temperature on 99.5NKN-0.5CuO + 0.6 wt% Nb2O5 solid and powder samples. The data were Rietveld refined. The solid sample underwent two polymorphic phase transitions at 300°C and 515°C; the latter was between two tetragonal phases: lattice parameters for the tetragonal phase (300-520°C) were a’ = c’ = 4.99557 Å, and b’ = 4.0363 Å; high temperature tetragonal (>500°C) exhibited a’ = c’ = 4.9519 Å, and b’ = 4.4941 Å. The powder sample of the same formulation exhibited more, smaller transformations. It was only orthorhombic at temperatures <140°C with a’ = c’ = 4.10680 Å, and b’ = 4.02620 Å. Above 140°C both orthorhombic and tetragonal phases were present. Another significant transformation occurred at 360°C where the structural unit cell parameters changed significantly. Parameter lengths are provided. P-E data was characterised by Pr = 19.9 μC/cm2 and EC = 13.5 kV/cm. Synchrotron X-ray diffraction analysis of 94 NKN-6LiTaO3 showed that tetragonal phase was present at 20-390°C, although an orthorhombic phase was identified at 20-200°C and again at 340-390°C just before the cubic transition temperature at 390°C. This is a new observation for NKN. A new and simple method for tape casting was developed to reduce powder wastage, enabling thick films of 50 μm to be cast. The reactive templated grain growth (RTGG) method was employed to orient 95NKN-5LiNbO3 and 94NKN-6LiNbO3 samples; CuO was utilised as a sintering aid. Pre-cursor BNN and NN template particles were produced using the molten salt synthesis (MSS) method, using a salt to oxide ratio of 1:1. Resulting NN particles were 15 μm wide and 0.5 μm thick. Eight layered 6LN + 0.4 wt% tapes produced using 10 wt% template particles resulted in 210 μm thick tapes with 67% orientation when sintered at 1150°C. Resulting properties include TC = 440ºC and TO-T = 70ºC, 25 kΩ resistance and capacitance 21.6 pF.

Submitted work deals with monitoring impact of thermal and electric ageing on the dielectric properties of insulating material NKN 0887. In the course of the experiment five sets of dielectric insulating materials were aged. The voltage range has been set from 1,5 kV till 2,2 kV and temperatures were 23 °C and 200 °C. The capacity and loss factor has been directly measured by RLC meter Agilent with attached electrode system. The electrode system operates on the principle of a plate capacitor. The values of relative permittivity and loss number has been calculated from values of capacity and loss factor. For easier confrontation has been frequency dependences of these values plotted in a chart. The Cole-Cole diagrams has been created and factors of Havriliak-Negami function has been calculated. Data has been compared with each other and the effect of ageing factors has been deduced.

The Master Thesis evaluates the energy demands of two types of family houses. The calculations are performed using the national calculation tool NKN II and the simulation software TRNSYS. The results of both methods are compared and their differences explained. Both calculation tools are compared from the user point view and finally their applicability for project designers is evaluated.

L'objectif de ce travail était l'élaboration par ablation laser pulsé (PLD) et la caractérisation de couches minces d'oxydes dans le système K-Nb-O, et plus précisément d'une phase de structure bronze de tungstène quadratique (TTB) sous forme de nanorods, potentiellement intéressante dans le contexte de la recherche de nouveaux piézoélectriques sans plomb. Malgré une forte compétition de croissance entre les différentes phases, l'étude approfondie des conditions de dépôt a montré la possibilité d'obtenir les phases KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB) et KNbO3, en films minces après une phase d’optimisation essentielle. Nous avons déterminé l'influence des conditions de dépôt sur la formation et la nanostructuration de ces composés en couches minces. En particulier, il a été démontré que la température et la composition de la cible PLD avaient une forte influence sur la croissance de la phase de structure TTB. Une étude plus approfondie de ces phases a révélé que toutes avaient une morphologie spécifique liée à leur structure anisotrope, que nous avons pu contrôler par la croissance épitaxiale sur les substrats SrTiO3 orienté (100) et (110). L'existence d'une activité piézoélectrique dans des couches minces de la phase TTB, mise en évidence par PFM, lui confère un intérêt certain. Cette phase TTB a également été obtenue dans le système Na-K-Nb-O, très connu pour ses propriétés piézoélectriques et ferroélectriques, ouvrant la voie sur de nouvelles recherches. / The purpose of this work was the elaboration by pulsed laser deposition (PLD) and the characterization of thin films of oxides in the K-Nb-O system, and more precisely that of a tetragonal tungsten bronze phase (TTB) as nanorods, of potential interest as a new lead free piezoelectric. In spite of a strong growth competition between the different phases, the detailed study of the deposition conditions showed that it is possible to obtain KNb3O8, K4Nb6O17, K6Nb10,88O30 (TTB ) and KNbO3 in thin films form after an important optimization step. We have determined the influence of these deposition conditions on the formation and the nanostructuration of these compounds as thin films. In particular, it was shown that the temperature and the PLD target’s composition has a strong influence on the growth of the TTB structure. A further study of these phases revealed that all have a specific morphology related to their anisotropic structure, that we have controlled by the epitaxial growth on the (100) and (110) SrTiO3 substrates. The existence of a piezoelectric activity in the TTB thin films, evidenced by PFM, gives a great interest to this phase. This TTB phase was also obtained in the Na-K-Nb-O system, well known for its piezoelectric and ferroelectric properties, opening the way to new research.