For 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (0.95NKN-0.05BT) ceramics sintered at 1040–1075°C, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075°C. The dielectric constant (ϵ3T∕ϵ3), electromechanical coupling factor (kp), and piezoelectric constant (d33) were considerably increased with increasing relative density and grain size. Evaporation of Na2O deteriorated the piezoelectric properties by decreasing the resistivity. To minimize Na2O evaporation, specimens were muffled with 0.95NKN-0.05BT powders during the sintering. Improved piezoelectric properties of d33=225pC∕N, kp=36%, and ϵ3T∕ϵ3=1058 were obtained for specimen sintered at 1060°C for 2h with muffling.

Mixtures of zinc metatitanate and rutile (ZnTiO 3 + xTiO 2 , where x = 0-0.5) have been prepared via the conventional mixed-oxide method. Centrifugal planetary milling with zirconia beads 1 mm in diameter produced very fine powders (mean particle size of 0.2 µm), which allowed the synthesis of ZnTiO 3 and sintering at temperatures <945°C, which is the decomposition temperature of ZnTiO 3 . Sintering of the mixtures was enhanced further by the addition of B 2 O 3 . Densities of >94% of the theoretical density have been attained for the specimens that were sintered at 875°C for 4 h with B 2 O 3 additions of <1 wt%. Microwave dielectric properties of the aforementioned compositions were as follows: dielectric constant of 29-31, normalized quality factor of 56000-69000 GHz, and a temperature coefficient of resonance frequency between −10 and +10 ppm/°C. Sintering was enhanced by the formation of a ZnO-B 2 O 3 liquid phase, which affected the microwave properties, because of variation in the phase composition.

The thermal stability and structural characteristics for gate stack structure of HfO2 dielectrics deposited by atomic-layer deposition (ALD) were investigated. The structural characteristics and chemical state of the HfO2 films in relation to the film thickness and postannealing temperature were examined by x-ray diffraction and x-ray photoelectron spectroscopy. An interfacial layer of hafnium silicate with an amorphous structure was grown on the oxidized Si substrate at an initial growth stage. The structural characteristics of the HfO2 films are closely affected by the interfacial layer and are depended on the thickness of the films. The 45 Å thick HfO2 film with an amorphous structure was changed into a polycrystalline structure after rapid temperature annealing of 750 °C for 5 min, while thicker films were grown into a polycrystalline structure of monoclinic or tetragonal crystal structure. The silicate layer grown at the interfacial region is not stable even at 700 °C under ultrahigh vacuum condition and changes into the silicide layers.

A dielectric ceramic comprised of (Zn 1−x Mg x )TiO 3 (x = 0 to x = 0.5) with low sintering temperature and promising microwave properties was prepared by applying a semichemical synthesis route and a microbeads milling technique. X-ray diffractometry and thermal analyses results indicated that the phase stability region of the hexagonal (Zn,Mg)TiO 3 extended to higher temperatures as the amount of magnesium increased. The dielectric properties in this system exhibited a significant dependence on the sintering conditions, especially near the phase decomposition temperature. From 950°C, the temperature compensation characteristics occurred as the phase composition changed from hexagonal (Zn,Mg)TiO 3 to two phases: (Zn,Mg) 2 TiO 4 and rutile. The magnesium content for zero temperature coefficient ( f ) was ∼3 mol% at 950°C; however, f increased with the sintering temperatures because of the shift of the decomposition temperature.

The orthorhombic structure of (Na0.5K0.5)NbO3 (NKN) ceramics was maintained when ZnO was added. NKN ceramics have a porous microstructure and dissolve when they are exposed to water. However, as ZnO was added, a dense microstructure was developed and deliquescence was not observed. The mechanical quality factor (Q m) and coercive field (E c) increased with the addition of ZnO, indicating that ZnO acted as a hardener in the NKN ceramics. The dielectric constant (ε T 3/ε o), piezoelectric constant (d 33) and electromechanical coupling factor (k p) increased when a small amount of ZnO was added, which might be due to the increase in density. The good dielectric and piezoelectric properties of ε T 3/ε o = 500, d 33 = 121 and k p=0.4 were obtained for the NKN ceramics with 1.0 mol% ZnO.