Antiferroelectricity and robust dielectric response owing to competing polar and antipolar instabilities in tetragonal tungsten bronze K2RNb5O15 ( R : rare-earth)

K2RENb5O15 (RE = Ce, Pr, Nd, Sm, Gd–Ho): A Family of Quasi-One-Dimensional Spin-Chain Compounds with Large Interchain Distance

“…The K 2 RENb 5 O 15 (RE = La–Ho) family of compounds are crystallized into the TTB structure; , most family members undergo a structural phase transition from space group P 4 bm to Ima 2 and then to P /4 mbm as the temperature increases . Considering that the RE 3+ ions in K 2 RENb 5 O 15 have the same lattice geometry independent of the P 4 bm or P /4 mbm symmetry, a representative, room-temperature crystal structure of K 2 NdNb 5 O 15 is presented in Figure a,b.…”

“…127) and polar P 4 bm (no. 100) at high- and low-temperature regimes, and the AFM–FE transition temperature ( T C ) ranges from ∼300 to ∼460 K, depending on the choice of RE 3+ ions. , Despite the well-studied crystal structure and related electronic properties, the lattice geometry of RE 3+ ions and their magnetic behaviors have not been unveiled, motivating the present study. Here, we report the synthesis and magnetic properties of this series of RE-based K 2 RENb 5 O 15 (RE = Ce–Ho) oxoniobates, in which the magnetic RE 3+ ions are unveiled to form a 1D uniform chain along the c -axis with an intrachain distance of d intra = c ∼ 3.89–3.92 Å and a large spatially separated interchain distance of a / 2 ∼ 8.79–8.87 Å in the ab -plane.…”

“…The RE-based tetragonal tungsten-bronze (TTB) structure K 2 RENb 5 O 15 (RE = La–Ho) compounds, an important family of ferroelectric (FE) materials, have been well studied for their interesting dielectric and nonlinear optic properties. − The previous crystal structure and temperature ( T )-dependent dielectric measurements reveal that most members of the K 2 RENb 5 O 15 (RE = La–Ho) family undergo two phase transitions from the paraelectric (PE) to antiferroelectric (AFE) to FE phases as a function of temperature . Correspondingly, they crystallize into the centrosymmetric space group of P/4 mbm (no.…”

Nonlinear dielectric response and positive dielectric tunability in antipolar CaTiSiO5

“…The starting materials were weighed and calcined at 900℃ for 2 h. Green chips of MLCCs with Pt-inner electrodes were prepared via existing MLCC processes. 26 After sintering at 1250-1300℃ for 2 h, MLCC samples (Figure 1B) were obtained. The effective electrode area and thickness of the dielectric layer were ~3 mm 2 and 22 μm, respectively.…”

Developing new antiferroelectric and ferroelectric oxides and chalcogenides within the A2BX3 family

“…A few common examples of solid-state FEs include the perovskites [21][22][23][24][25][26][27], Ruddlesden-Popper phases [28,29], Aurivillius and Dion Jacobson compounds [30][31][32][33][34], boracites [35,36], tellurides [37,38], and K 2 SeO 4 -type materials [39,40]. Solidstate AFEs also include the perovskites [41][42][43][44][45][46], as well as sulfoaluminates [47], ZrO 2 , and HfO 2 [48,49], orthorhombic ABC semiconductors [2,7], Bi 2 SiO 5 [50,51], and tungsten bronzes [52]. There are a preponderance of example FEs and AFEs that include oxides, sulfides, and selenides, and multiple examples where a variety of experimental techniques such as doping, film growth, strain engineering, confinement, and compositional tuning has resulted in the stabilization of new phases and resulted in enhanced material performance [17,18,43,49,53].…”