Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr_9−xPb_xCe₂Ti₂O₃₆(x = 0−9) Ceramic System

Abstract

Sr9−x Pb x Ce2Ti12O36 system is derived from the perovskite SrTiO3 and its chemical formula can be written as (Sr1−y Pb y )0.75Ce0.167TiO3. We investigated dielectric response of Sr9−x Pb x Ce2Ti12O36 ceramics (x = 0−9) between 100 Hz and 100 THz at temperatures from 10 to 700 K using low- and high-frequency dielectric, microwave (MW), THz, and infrared spectroscopy. We revealed that Sr9Ce2Ti12O36 is an incipient ferroelectric with the R3̅c trigonal structure whose relative permittivity ε′ increases from 167 at 300 K and saturates near 240 below 30 K. The subsequent substitution of Sr by Pb enhances ε′ to several thousands and induces a ferroelectric phase transition to monoclinic Cc phase for x ≥ 3. Its critical temperature T C linearly depends on the Pb concentration and reaches 550 K for x = 9. The phase transition is of displacive type. The permittivity ε′ follows the Barrett formula (typical for quantum paraelectrics) in samples with x ≤ 2. The MW dispersion is lacking and quality factor Q is high in samples with low Pb concentration, although the permittivity is very high in some cases. However, because of the lattice softening, the temperature change of the permittivity is rather high. The best MW quality factor was observed for x = 1: Q f = 5800 GHz and ε′ = 250. Concluding, the dielectric properties of Sr9−x Pb x Ce2Ti12O36 are similar to those of Ba1−x Sr x TiO3 so that this system can be presumably used as an alternative for MW devices or capacitors.

Microwave dielectric properties of flexible butyl rubber–strontium cerium titanate composites

“…This may be due to the incipient ferroelectric nature of SCT. Incipient ferroelectrics are characterized by increasing permittivity on cooling due to the softening of the lowest frequency polar optical phonon 17. Recently Subodh et al have reported a similar behavior in polyethylene–Sr 9 Ce 2 Ti 12 O 36 composites 18…”

“…Among various elastomer materials, butyl rubber has excellent dielectric properties, such as low relative permittivity (ε r ≈ 2.4) and low dielectric loss (tan δ ≈ 10 −3 ), mechanical flexibility, good weathering resistance, biocompatibility etc 9. Recently Sr 2+n Ce 2 Ti 5+n O 15+3n ( n = 0–10) based ceramics and their composites has been studied extensively due to their high relative permittivity and relatively low dielectric loss 15–19. Sr 2 Ce 2 Ti 5 O 15 (SCT) ceramic has a high relative permittivity of 112, low loss of 10 −4 at 7 GHz and a low CTE of 1.7 ppm °C −1 15, 16.…”

Piezoelectric and ferroelectric properties of new Pb9Ce2Ti12O36 and lead-free Ba2NdTi2Nb3O15 ceramics

“…The measured temperature range was well below the ferroelectric phase transition temperature (T C =277°C). The temperature dependence of the dielectric response and critical temperature T C =277°C was determined elsewhere [7]. The decrease in the coercive field with increasing temperature in the temperature range between 25°C and 70°C was lower than 8% (Fig.…”

“…of Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology Trivandrum, India. The synthesis procedure and properties characterizations were described [7]. Disc shaped samples with a diameter of 9 mm and a thickness of 0.5 mm or 1 mm were used for the hysteresis measurements and for the resonance measurements discs with a diameter of 15 mm and a thickness of 1 mm were used.…”

“…The temperature and frequency dependence of the complex permittivity of BNTN ceramics in the low-and high-frequency range were reported [6] and the dielectric and structural data of Pb 9 CTO were summarized [7]. At room temperature tetragonal BNTN and monoclinic Pb 9 CTO ceramics were assigned the non centrosymmetric space groups P4bm and Cc, respectively.…”