Effects of Calcium Titanate and Strontium Titanate Additives on Microstructure and Microwave Dielectric Properties of Tellurium Oxide

• Main Authors: Yen-Ling Liu, 劉妍伶
• Other Authors: Chi-Yuen Huang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/58994573466922782297

碩士 === 國立成功大學 === 資源工程學系碩博士班 === 97 === Recently, tellurium dioxide has been explored as a low-melting end member of dielectric ceramic compounds. Therefore, a number of tellurium-based low-temperature dielectric resonator materials with excellent dielectric constant and quality factor have been reported. However, most of these materials have a high τf and are not able to apply. This study is focus to compensate the negative temperature coefficient of TeO2 by adding of CaTiO3, SrTiO3 and investigate the effects on microstructure and dielectric properties. This study shows pure TeO2 ceramics with >95% theoretical density can be produced by sintering at 640℃ for 4 hours. The TeO2 ceramic has a dielectric constant (εr) of 28.41, quality factor (Q × f) of 34700 GHz (at 12.94 GHz) and temperature coefficient of resonant frequency (τf) of -101.81 ppm / ℃. In TeO2+x wt% CaTiO3 system by using X-ray powder diffractiometer, Raman spectroscopy, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) of Energy Dispersive Spectrometer (EDS) analysis results show that adding CaTiO3 to TeO2 generates the formation of TiTe3O8 and CaTe2O5. As the increasing of CaTiO3 content, the study shows the dielectric constant and quality factor increase. Addition 10 wt% CaTiO3 improves the τf to -3.24 ppm / ℃ with εr of 28.65 and Q × f value of 15600 GHz (at 10.98GHz) when sintered at 640℃ for 8 hours. In TeO2+x wt% SrTiO3 system by using X-ray powder diffractiometer, Raman spectroscopy, and Scanning electron microscopy (SEM) of Energy Dispersive Spectrometer (EDS) analysis results show that adding SrTiO3 to TeO2 generates the formation of TiTe3O8 and SrTe2O5. As the increasing of SrTiO3 content, the study shows the dielectric constant and quality factor have similar values. Because of the dielectric constant and quality factor are influenced by producing a liquid phase in the densification process. Addition 15 wt% SrTiO3 improves the τf to -3.81 ppm / ℃ with εr of 26.58 and Q × f value of 12400 GHz (at 11.08GHz) when sintered at 610℃ for 8 hours.