Barium polytitanate dielectric resonators for microwave wireless communication

The technology advancement of wireless communication has been made possible in part with recent advances in miniaturization of microwave circuits by using high-permittivity, temperature-stable, low-loss dielectric resonators. An important dielectric resonator material is {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} because of its outstanding microwave dielectric properties. However, {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} has been a difficult phase to form without dopants. Disagreement about the ability to form phase-pure {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} has been reported in the literature. The objective of the present thesis was to study the fabrication of {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} as well as other barium polytitanate, using various thermal schedules and chemical modifications. The optimization of microwave dielectric properties, development of microstructure, and reaction mechanisms amongst starting materials were also researched.; The effects of solid solution additives, namely Zr and Sn, their concentration, and thermal processing schedule on microstructure evolution and microwave properties of barium polytitanates were studied. Dielectric resonators of high quality factor (13900 at 3 GHz), dielectric constant (39.3), and near zero temperature coefficient of resonance frequency (1.3 ppm/{dollar}spcirc{dollar}C between 20-60{dollar}spcirc{dollar}C) were successfully fabricated. Extended heat treatment (16 vs. 6 h at 1390{dollar}spcirc{dollar}C) resulted in volatilization of grain boundary liquid phase, leading to more porous resonators, having correspondingly lower permittivities. Increasing dopant concentration resulted in minor increases in quality factor, with Zr-doping leading to slightly higher values (maximum: 13900). Increasing measurement temperature degraded the quality factor, most precipitously for {dollar}rm BaTisb4Osb9.{dollar} The temperature coefficient decreased with increasing ZrO{dollar}sb2{dollar}-substitution, but was largely unaffected by SnO{dollar}sb2{dollar} concentration.; Time-efficient thermal schedules for sintering ZrO{dollar}sb2{dollar}- and SnO{dollar}sb2{dollar}-doped {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} resonators to minimum porosity were developed using a shrinkage rate controlled dilatometer. The sintering schedules were formulated which circumvented pore formation via grain boundary/triple point liquid phase volatilization. A densification rate (0.5 %/min) for the early stages of sintering which minimized intragranular porosity was chosen. For the later stages of sintering, a densification rate (0.01 %/min) which minimized specimen slumping via liquid phase permitted sintering to high density. These schedules were successfully upscaled to heat treatment in a conventional furnace. The dielectric constants, quality factors, and selected temperature coefficients of 0.82 mol% and 1.64 mol SnO{dollar}sb2{dollar}-, and 1.64 mol% ZrO{dollar}sb2{dollar}-doped monophase {dollar}rm Basb2Tisb9Osb{lcub}2O{rcub}{dollar} are reported.; Sn{dollar}sp{lcub}4+{rcub}{dollar}-doped and undoped barium polytitanates pellets were sintered at 1360 and {dollar}1390spcirc{dollar}C for 5 h. Dilatometry studies implied that SnO{dollar}sb2{dollar} additions facilitated a greater fraction of reaction to occur in the solid state. Intermediate chemical reactions amongst the starting materials to form {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} and {dollar}rm BaTisb4Osb9{dollar} were identified as a function of temperature.; {dollar}rm Basb2Tisb9Osb{lcub}20{rcub}{dollar} compacts were reaction sintered from a pressed powder mixture of BaTiO{dollar}sb3{dollar} and TiO{dollar}sb2,{dollar} without solid solution additives. Specimens heated using an infrared furnace at {dollar}500spcirc{dollar}C/min to {dollar}1250spcirc{dollar}C for 2 h developed a microstructure with {dollar}sim{dollar}64 vol% {dollar}rm B...