Ferroelectricity in (CH₃NHCH₂COOH)₃·CaCl₂

Abstract

Tris-sarcosine calcium chloride, (CH₃NHCH₂COOH)₃·CaCl₂, is ferroelectric below the Curie point, 127°K, where the dielectric constant, ε_b, at low frequencies shows a sharp peak. The dielectric constants ε_a and ε_c. do not show any noticeable anomaly at the Curie point. The dielectric measurement at a microwave frequency of 9.4 Gc/s indicates that there is a marked dielectric dispersion in the Curie temperature region. The spontaneous polarization is 0.27 μCoul/cm² at 78°K. The high-temperature phase is orthorhombic with space group P_nma and a=9.153 Å, b=17.48 Å, c=10.28 Å at room temperature. The low-temperature phase may possibly be orthorhombic with point group C_2v. The measurement of specific heat as a function of temperature yields δS=(0.38±0.04) cal/mole·degree. The results are discussed in comparison with those of some ferroelectrics such as (glycine)₃·H₂SO₄.