Microwave Dielectric Properties of RE_1−xRE^′_xTiNbO₆ [RE = Pr, Nd, Sm; RE′= Gd, Dy, Y] Ceramics

Abstract

The microwave dielectric properties of rare‐earth titanium niobates can be tailored by preparing solid‐solution phases between RETiNbO6 [RE = Pr, Nd, Sm] and RE′TiNbO6 [RE′= Gd, Dy, Y] microwave dielectric ceramics. Dielectric ceramics based on solid‐solution phases RE1−xRE′xTiNbO6 are prepared by the conventional solid‐state ceramic route for different values of x. The ceramic samples are characterized by XRD, SEM, and microwave methods. Ceramics based on RETiNbO6 belonging to aeschynite group show a positive value of τf, and those based on RE′TiNbO6 belonging to the euxenite group have a negative value of τf. The solid‐solution phases between aeschynites and euxenites show intermediate dielectric constant and τf values. The results indicate the possibility of tailoring the microwave dielectric properties by varying the composition of solid‐solution phases. The range of solid solubility of euxenites in aeschynites and aeschynites in euxenites are different for different rare‐earth ions. The ceramics have low sinterability and a high dielectric loss factor near the vicinity of aeschynite to euxenite transition. The value of dielectric constant changes abruptly close to the transition point. The abrupt variation in microwave dielectric properties indicate a first‐order phase transition at x= 0.86 in Pr1−x Gd xTiNbO6, x= 0.48 in Nd1−x Dy xTiNbO6 and x= 0.27 in Sm1−xY x TiNbO6 ceramics. The dielectric constant and the sign of τf of the solid‐solution phases are found to depend on the average ionic radius of the rare‐earth ions in RE1−xRE′xTiNbO6. The euxenite to aeschynite phase transition occurs at an average ionic radius of 0.945 Å in all three systems of solid‐solution phases.

Fabrication and characterization of xPrTiTaO6(1−x)YTiNbO6 microwave ceramic composites

“…Dielectric constant varies from 20.20 to 37.50 and f varies from −45.07 to +42.81 ppm/ • C. For 50-50 composition sintered at 1380 • C, the f is minimum, i.e., −1.9 ppm/ • C and ε r is 33.78. There is a possibility of nonlinear variation in dielec- tric constant and f when the sample is in the region of change of symmetry from aeschynite to euxenite [12]. Hence the composite ceramic 50PTT of this series is the most suitable material as a dielectric resonator.…”

Atomistic simulation of the crystal structure and bulk properties of (, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er and Yb) compounds

“…On the other hand, highest dielectric quality factors have been found in AðB 0 1=3 B 00 2=3 ÞO 3 ceramic systems, mainly BaðMg 1=3 Nb 2=3 ÞO 3 and BaðMg 1=3 Ta 2=3 ÞO 3 [5,6]. More recently, oxides containing rare earth ions such as AðRE 1=2 M 1=2 ÞO 3 [7][8][9][10][11][12] and REðTiMÞO 6 [13][14][15][16][17][18], where A is commonly an alkaline earth metal, RE is an yttrium or rare-earth ion and M is a transition metal (usually Ta þ5 or Nb þ5 ), have been extensively studied showing good properties for microwave applications.…”

Synthesis and characterization of thermally stable, high Q, NdxY1−xTiTaO6 dielectric resonators

“…The principal difference between Ln 3+ in these structures is that in aeschynite orthorhombic structure they lie in closely connected chains where as in euxenite orthorhombic structures they lie on densely packed parallel planes [21]. Solomon et al [22] and Surendran et al [23,24] reported that by making a suitable solid solutions of both aeschynite and euxenite structures, it is possible to get compositions having low τ f and desirable microwave dielectric properties. Recently Oishi et al [25] reported the effects of Ta substitution for Nb and Zr substitution for Ti on the microwave dielectric properties and crystal structure of Sm(Nb 1−x Ta x )(Ti 1−y Zr y )O 6 ceramics.…”