L. Nedelcu

Ba/sub 1-x/Sr/sub x/TiO/sub 3/ ceramics for tunable microwave devices

The paper describes the investigations of Ba_1-xSr_xTiO₃ ceramic materials prepared by solid-state reaction techniques. The addition of MgO and MnO₂ improves sintering process and decreases the dielectric loss. The materials exhibit a dielectric constant epsiv_r~1000 and low loss tandelta~1O ^-3 at microwave frequencies

Dielectric ceramics based on the ZrO/sub 2/-SnO/sub 2/-TiO/sub 2/ ternary system for microwave and millimeter wave applications

This work describes the investigations of (Zr/sub 0.8/Sn/sub 0.2/)TiO/sub 4/ compounds prepared by solid-state reaction techniques. The effect of La/sub 2/O/sub 3/, ZnO and NiO addition on microwave dielectric properties was investigated. The samples were sintered at temperatures T/sub s/=1280 -1400 /spl deg/C. The materials exhibit a dielectric constant /spl epsiv//sub r//spl sim/36 and high values of the Q/spl middot/f product from 30,000 to 55,000 at microwave frequencies. The measured temperature coefficient of the resonance frequency /spl tau//sub f/ takes values in the range (-2/spl divide/+4) ppm//spl deg/C.

BNT ceramics in paraelectric phase: dielectric properties

The paper describes the investigations of Nd doped barium titanate (BNT) ferroelectric ceramic materials prepared by solid state reaction techniques. The decrease of the Curie temperature with the increase of the Nd/sub 2/O/sub 3/ concentration from 0 to 28 wt % was observed. High density values of BNT ceramics were obtained by adding 0.5 mol % PbO substitutional for BaO. The samples were sintered at temperatures T/sub s/=1200+1260/spl deg/C. At room temperature, the materials are in paraelectric phase, suitable for high frequency applications.