Phase diagram and phase transitions in ferroelectrictris-sarcosine calcium chloride and its brominated isomorphs

Autor:	Donald M. Evans, U. Straube, V. H. Schmidt, James F. Scott, Michael A. Carpenter, S. P. P. Jones, Simon A. T. Redfern
Rok vydání:	2011
Předmět:	Resonant ultrasound spectroscopy Phase transition Materials science Quantum critical point Doping Analytical chemistry ddc:530 Dielectric Condensed Matter Physics Ferroelectricity Electronic Optical and Magnetic Materials Phase diagram Solid solution
Zdroj:	Physical Review B. 83
ISSN:	1550-235X 1098-0121
DOI:	10.1103/physrevb.83.094102
Popis:	Tris-sarcosine calcium chloride [(TSCC), (CH3NHCH2COOH)3CaCl2] is a uniaxial ferroelectric (FE) with a displacive second-order phase transition near Tc=130 K. A continuous range of solid solutions can be made by substituting Br for Cl, which lowers Tc to 0 K at ∼72% Br. Such a quantum critical point differs from that in pseudocubic FEs, such as O-18 SrTiO3 or doped KTaO3. For many years, this system was thought to have only two phases, paraelectric and FE, at ambient pressure. However, we find from dielectric and resonant ultrasound spectroscopy that there are four phase transitions in TSCC and in TSCC:Br (for 0 T > 185 K, disordered; Pnma with Z=4(D2h16)185 K>T>130 K (ordered); Pn21a with Z=4(C2v9)130 K>T>64 K (FE); P21a (C2h5) with Z =4, 64 K > T > 45 K (not AFE); T 500 K) is hypothesized to be D6h3(P63/mcm) with Z =2, but the samples decompose first at 503 K (230 °C).
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::30474a9c58ad7ae44589a16307527358 https://doi.org/10.1103/physrevb.83.094102 Zobrazit plný text záznamu