High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. In this context, the observation of anomalously high dielectric constant (>104) in the body-centered cubic perovskite-related (Space group Im3) material Calcium Copper Titanate ((CaCu3Ti4O12)(CCTO)) over wide frequency (100 Hz – 1MHz at RT) and temperature (100 – 600 K at 1 kHz ) ranges has attracted a great deal of attention. However, high dielectric constant in CCTO is not well understood yet, though internal barrier layer capacitor (IBLC) mechanism is widely been accepted. Therefore, the present work has been focused on the preparation and characterization of CCTO ceramic and to have an insight into the origin of high dielectric constant. Influence of calcination temperature, processing conditions, microstructure (and hence grain size), composition, doping etc on the electrical characteristics of CCTO ceramics were investigated. Electrical properties were found to be strongly dependent on these parameters. The dielectric constant in CCTO was observed to be reduced considerably on substituting La+3 on Ca+2 site. The formation temperature of CCTO was lowered substantially (when compared to conventional solid-state reaction route) by adopting molten-salt synthesis. The dielectric loss in CCTO was reduced by incorporating glassy phases at the grain boundary. Potential candidates for the practical applications such as charge storage devices, capacitors etc, with dielectric constant as high as 700 at 300 K was accomplished in a three-phase percolative composite fabricated by incorporating Aluminium particle into CCTO-epoxy composite. Polycrystalline CCTO thin films with dielectric constant as high as ~ 5000 (1 kHz and 400 K) were fabricated on Pt(111)/Ti/SiO2/Si substrates using radio frequency magnetron sputtering. Effect of sintering conditions on the microstructural, ferroelectric and varistor properties of CCTO and LCTO ceramics belonging to the high and low dielectric constant members of ACu3M4O12 family of oxides were investigated in detail and are compared. Ferroelectric-like hysteresis loop (P vs E) and weak pyroelectricity were observed in CCTO and plausible mechanisms for this unusual phenomenon have been proposed.

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Abstract The purpose of this task is to synthesize a dielectric substrate material through a sintering process, which can be used for non-invasive physiological sensor development. Low loss, high dielectric constant ceramic material is used. Sintering process is employed to ensure stable structure and homogeneous dielectric properties of the substrate. Samples were prepared with TiO2 and in combination with CuO and Al2O3. All samples were measured and validated in 500 MHz to 20 GHz frequency range. Characterization measurements were performed with a Vector Network Analyzer, FieldFox N9918A, and connected to Keysight, open ended coaxial probe and performance probe. Reflection based measurement method was used due to its simplicity, speed and requirement of wideband data. The dielectric measurement results of developed samples show non-frequency dispersive behaviour, high dielectric constant and data was also selected at 2.45 GHz in aligned to the industrial, scientific and medical band. The resulting measurements show the highest dielectric constant of 16.6 at 2.45 GHz with a very low loss behaviour. / Målet är att syntetisera ett material, genom sintringsprocess, som kan användas som ett dielektriskt substrat för utveckling av sensorer. Det dielektriska materialet har keramisk materialstruktur och innehar högt dielektricitetskonstant med låga dielektriska materialförluster. Denna uppgift kräver att dielektriska materialet ska vara stabilt och inneha isotropiska egenskaper efter att genomgått sintringsprocess. Proverna förberedes med TiO2 och även i kombination med TiO2 tillsammans med CuO och Al2O3. Proverna mäts i frekvensområdet 500 MHz till 20 GHz. Mätningarna utförs med Vector Network Analyzer, FieldFox N9918A från Keysight. Resultat som visas och jämförs i arbetet är tagna vid 2.45 GHz eftersom det används och är standardiserat för medicinskt frekvensband. Högsta uppmätta dielektricitetskonstant har värdet av 16,6. Resultaten visar även låga förluster i dielektrikumet.