Dielectric properties of single crystals of LaGaO3 have been measured at low frequencies as well as in the microwave region over a wide temperature range. Measurements performed on two crystal orientations, viz. (001) and (110), show dielectric anomalies at a transition near 145 °C. Dielectric anisotropy below, but not above, 145 °C confirm the previously reported orthorhombic symmetry at room temperature and rhombohedral symmetry above 145 °C. Domain wall motion which arises as a result of a phase transition has been observed around 145 °C.
A dynamic method for quantitatively determining the pyroelectric coefficient of thin films is presented. The technique offers several advantages over competitive techniques. These advantages include, the ability to distinguish between reversible (pyroelectric) and irreversible thermally induced currents, a facility to study time-varying pyroelectric responses, more rapid determinations at room temperature, and higher measurement precision. Details of the mechanical and electrical design of the instrument are given, together with examples of experimental data which illustrate the working operation of the equipment.
Acetylacetonate (acac) complexes of titanium and zirconium
were examined for their reactivity with alcohols and diols.
Alcoholysis of the acac ligand resulted in the formation of
acetone and the acetyl ester of the alcohol, with the concomitant
formation of the metal alkoxide. The Zr(acac)4
complex was more reactive than the
Ti(acac)2(OR)2 complexes (OR =
alkoxide) while the reactivity of the alcohols increase in the order
tertiary < secondary ≪
primary.
A film of PZT-PMN composition was fabricated by the deposition of fine powder entrained in airflow on to a substrate at the temperature of 20 °C. The particle flow generated by a jet mill desintegrator circulated inside the cylindrical substrate tube producing a build up on the internal surface of the cylinder. The resulting film, 70 – 150 µm thick was mechanically removed (delaminated) from the substrate and sintered at 800 °C. Microscopic examination of the green and sintered films revealed a very dense microstructure with a grain size for the sintered film of 0.2 – 0.8 µm. The relative permittivity at 1 kHz was about 100 before sintering and 2000 after sintering (unpoled). The permittivity of the sintered film had the same value as for bulk ceramic samples fabricated from the same powder using conventional isostatic pressing technique and sintered at 1250 °C to 97 % of the theoretical density.The study showed that the properties of the green body produced by the powder deposition process were superior to the properties of bulk samples prepared by the conventional pressing procedure. The method provides a route for the formation of a fine grain microstructure, and a sintering temperature 450 °C lower than the accepted sintering temperature for this PZT-PMN composition.
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