Growth and Characterization of Ba₂LnFeNb₄O₁₅ (Ln = Pr, Nd, Sm, Eu) Relaxor Single Crystals

Abstract

Ba2LnFeNb4O15 (Ln = Pr, Nd, Sm, and Eu) single crystals were grown from high-temperature solution under controlled atmosphere. Chemical, structural, and dielectric characterizations were performed on four crystals with tetragonal tungsten bronze (TTB) structure. The main difference between the four crystals’ compositions is the proportion of rare-earth, as well as vacancies, located in the square site. All crystals displayed an incommensurately modulated structure at room temperature in the paraelectric state. The corresponding basic structures were refined using the P4/mbm space group (R = 0.0274; 0.0416; 0.0328; 0.0357 for Ln = Pr, Nd, Sm, and Eu, respectively). Examination of the structural parameters confirmed the central role played by square-shaped channels in the crystal chemistry of these materials. All crystals display a relaxor behavior with T m (1 MHz) ranging from 110 to 270 K. The chemical, structural, and physical properties of the crystals are discussed and compared, for the latter, with those of corresponding ceramics.

Dielectric properties of tetragonal tungsten bronze films deposited by RF magnetron sputtering

“…This phenomenon could be related to the one observed in corresponding ceramics and single-crystals, in which the insertion of smaller rare earths (i.e. Nd or Eu instead of La) leads to and off-stoichiometry that could involve oxygen losses, which can be induced during the processing [14,30,31]. It was reported that the leakage current of oxide films could be reduced by activated oxygen annealing [39].…”

Elastic and anelastic relaxations accompanying relaxor ferroelectric behaviour of Ba6GaNb9O30 tetragonal tungsten bronze from resonant ultrasound spectroscopy

“…In recent years, the research dedicated to novel TTB ferroelectric and ferroelectric-related (i.e., relaxors) materials has undergone a revival, with Ba 6 FeNb 9 O 30 (BFNO) as a starting point; many related compositions [28][29][30][31] or solid solutions, usually containing lanthanides [32][33][34][35][36], were studied. Arnold and Morrison [5], and subsequently Liu et al [37], showed that these compounds display relaxor-type behaviour [38][39][40], with the peak maxima in the dielectric permittivity occurring in the temperature range 130-150 K. Earlier data indicated that BFNO is not electrically homogeneous [34], with oxygen vacancy gradients due to the variable oxidation state of Fe (Fe 3?…”

Temperature‐stable unfilled tungsten bronze dielectric ceramics: Ba3.5Sm1.5Fe0.75Nb9.25O30

“…These impurities are also found in Ba 4 Ln 2 Fe 2 Nb 8 O 30 ceramics. 20,21 Figure 2 presents the surface morphology of the sintered ceramic exhibiting homogeneous microstructure with rod-like grains and low porosity. The relative density of the ceramic is 95.2% (the relative density is calculated by the ratio of apparent density and true density).…”