The effect of partial isovalent substitution in the A-sublattice on MW properties of materials based on Ba6-xLn8 +2x/3Ti18O54 solid solutions

Investigations of materials based on the three systems: (Ba1-yPby)(6-x)La8+2x.3Ti18O54, (Ba1-xPby)(6-x)Nd8+2x.3Ti18O54, and (Ba1-yCay)(6-x)Ln(8 + 2x.3)Ti(18)O(54) revealed that a partial isovalent substitution in cation sublattices allows the control of the electrophysical parameters of microwave dielectrics. The investigations were carried out over a wide range of x values. Data on the relationship between the crystal-cell parameters and the microwave dielectric properties (epsilon, Q. and t(f)) have been obtained and related to the size of the isovalent ion residing at crystallographic sites in the A-sublattice. Based on the data obtained, a non-random distribution of Ca2+ arid Pb2+ ions on different A-sites as a function of their concentration in different systems was concluded. Various temperature-stable microwave dielectrics, based on the above three systems, have been synthesized and shown to exhibit excellent MW properties. (C) 2001 Elsevier Science Ltd. Ali rights reserved.