Dielectric Characteristics of (A_1/2 ¹⁺·A_1/2 ³⁺)TiO₃ Ceramics at Microwave Frequencies

Abstract

We have investigated the dielectric characteristics at microwave frequencies of perovskites with the formula (A1/2 1+·A1/2 3+)TiO3, (where A1+ represents an alkali metal from the lithium to potassium series and A3+ represents a member of the lanthanide series from lanthanum to lutetium). It was found for the first time that in the case of Li1+ substitution at the A1+ site, the larger the ionic radius of the element which substituted at the A3+ site, the higher the dielectric constant was and the greater the negative shift of the temperature coefficient of resonant frequency was. For the (1-x)(Li1/2 1+·Sm1/2 3+)TiO3-x(Na1/2 1+·Sm1/2 3+)TiO3 system at 3 GHz, high dielectric properties of εr=81, Q=2050 and τf=+17ppm/ °C were obtained when x=0.4.

Development and Dielectric Properties of Ba2−xSrxDyTaO6(x=0, 1, and 2) Substrates for YBa2Cu3O7−δFilms

“…This may be due to the fact that substitution of Sr at the Ba sites decreases the unit cell size and hence polarization is reduced. A similar result was also observed in (A> A> )TiO compounds (21). The lattice matching of the substrate with YBCO superconductor is an important criterion for the epitaxial growth of superconducting films on single crystal substrates.…”

Dielectric Properties and Sintering Characteristics of CaTiO3-(Li1/2Nd1/2)TiO3 Ceramics

“…Hitherto, several materials with high dielectric constant have been reported and most of them are focused on plural elements system including TiO 2 , such as BaO-Nd 2 O 3 -TiO 2 -Ta 2 O 5 [1,2], BaO-Sm 2 O 3 -TiO 2 [3,4], CaO-Li 2 O-Ln 2 O 3 -TiO 2 [5][6][7][8][9], or (A +1 1/2 A +3 1/2 )TiO 3 system [10]. Among of these materials, compositions with perovskite structure based on (A +1 1/2 A +3 1/2 )TiO 3 system or CaTiO 3 system have superior microwave properties: ε = 81, Q f = 6150 GHz, τ f = +17 ppm/ • C for 0.6(Li 1/2 Sm 1/2 )TiO 3 -0.4(Na 1/2 Sm 1/2 )TiO 3 ceramics [10], ε = 110, Q f = 4500 GHz, τ f = +7 ppm/ • C for CaOSrO-Li 2 O-Ln 2 O 3 -TiO 2 (Ln = Sm, Nd) system [5], ε108,Q f = 17200 GHz in (Ca 1−x Nd 2x/3 )TiO 3 system [11] and 0.67Ca 2/5 Sm 2/5 TiO 3 -0.33Li 1/2 Sm 1/2 TiO 3 ceramics with ε = 95.5, Q f = 7200 GHz, τ f = 0 ppm/ • C [9]. CaTiO 3 and (A +1 1/2 A +3 1/2 )TiO 3 are promising materials with high dielectric constant and high Q f value.…”

“…CaTiO 3 is of orthorhombic perovskite structure [11], Li 1/2 Ln 1/2 TiO 3 (Ln = Sm, Nd) is of orthorhombic perovskite structure (or cubic perovskite structure) [10], both have high dielectric constant and show positive and negative temperature coefficient of frequency, respectively, but both of them have the same drawback: poor sintering behavior.…”

Circularly Polarized Dielectric‐Loaded Antennas: Current Technology and Future Challenges

“…Temperature-stable compounds based on Li 2 O-CaO-RE 2 O 3 -TiO 2 with such permittivities do exist but their Q values are too low (<3000@1 GHz) to act as effective antenna cores. [16] The decrease in Q with permittivity is self-evident from Figure 6 and is fundamental to the physics of dielectrics. [10] Even if such compounds could exist the equivalent D-LQH design would have greater volumetric efficiency.…”