Compositions from TiO2-TeO2 tie line were characterised using X-ray powder
diffraction (XRD), scanning electron microscopy (SEM), transmission electro
n microscopy (TEM) and dilatometry. Results show that the only binary compo
und existing on the tie line is TiTe3O8, Single-phase TiTe3O8 was synthesis
ed at 700 degreesC in air and sintered at 720 degreesC to similar to 95% of
theoretical density. Such ceramics exhibit a relative permittivity of 50,
a Oxf-value of 30,600 GHz and a temperature coefficient of resonant frequen
cy (tau (f)) of +133 ppm/degreesC, measured at similar to5 GHz. The concent
ration of structural defects in the TiTe3O8 grains is negligible which make
s the dielectric properties of TiTe3O8 ceramics insensitive to variations i
n the heat-treatment conditions. The TiTe3O8 compound is chemically compati
ble with TeO2, which displays a negative temperature coefficient of resonan
t frequency (a relative permittivity of 19.3, a Qxf-value of 30,000 GHz and
a temperature coefficient of resonant frequency of -119 ppm/degreesC for T
eO2 ceramics with similar to 20% porosity) and can be used for compensation
of the temperature coefficient of resonant frequency of the TiTe3O8 compou
nd. Ceramics from the TiTe3O8-TeO2 subsystem can be sintered to > 97% of th
eoretical density at temperatures as low as 670 degreesC, which together wi
th the fact that the ceramics exhibit a highly tunable rf, relative permitt
ivity around 30 and a Qxf-value of similar to 22,000 GHz suggests a potenti
al for use in LTCC technology. (C) 2001 Elsevier Science Ltd. All rights re
served.