Publications

Abstract not provided.

Thermal properties of niobium-modified PZT95/5(1.8Nb) and PSZT ceramics used for the ferroelectric power supply have been studied from -100 C to 375 C. Within this temperature range, these materials exhibit ferroelectric-ferroelectric and ferroelectric-paraelectric phase transformations. The thermal expansion coefficient, heat capacity, and thermal diffusivity of different phases were measured. Thermal conductivity and Grueneisen constant were calculated at several selected temperatures between -60 C and 100 C. Results show that thermal properties of these two solid solutions are very similar. Phase transformations in these ceramics possess first order transformation characteristics including thermal hysteresis, transformational strain, and enthalpy change. The thermal strain in the high temperature rhombohedral phase region is extremely anisotropic. The heat capacity for both materials approaches to 3R (or 5.938 cal/(g-mole*K)) near room temperature. The thermal diffusivity and the thermal conductivity are quite low in comparison to common oxide ceramics, and are comparable to amorphous silicate glass. Furthermore, the thermal conductivity of these materials between -60 C and 100 C becomes independent of temperature and is sensitive to the structural phase transformation. These phenomena suggest that the phonon mean free path governing the thermal conductivity in this temperature range is limited by the lattice dimensions, which is in good agreement with calculated values. Effects of small compositional changes and density/porosity variations in these ceramics on their thermal properties are also discussed. The implications of these transformation characteristics and unusual thermal properties are important in guiding processing and handling procedures for these materials.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Low temperature co-fire ceramic (LTCC) materials technology offers a cost-effective and versatile approach to design and manufacture high performance and reliable advanced microelectronic packages (e.g., for wireless communications). A critical issue in manufacturing LTCC microelectronics is the need to precisely and reproducibly control shrinkage on sintering. Master Sintering Curve (MSC) theory has been evaluated and successfully applied as a tool to predict and control LTCC sintering. Dilatometer sintering experiments were designed and completed to characterize the anisotropic sintering behavior of green LTCC materials formed by tape casting. The resultant master sintering curve generated from these data provides a means to predict density as a function of sintering time and temperature. The application of MSC theory to DuPont 951 Green Tape{trademark} will be demonstrated.