Noncentrosymmetric coordination networks

In addition to electronic distortions, salt inclusion materials, and borates, coordination networks that are acentric have also been designed. The design and synthesis of NCS coordination networks have been developed by Rosseinsky et Lin et and others. ° ° All of 

NCS chiral coordination frameworks have also been designed and synthesised by Lin et who utilised the diamondoid network 

The pyroelectric effect may be defined as the change in spontaneous polarisation, s, as a function of temperature. The symmetry requirements for pyroelectricity are far more restrictive compared with SHG and piezoelectricity. To exhibit a spontaneous polarisation, the material in question must crystallise in one of ten polar crystal classes (1, 2, 3, 4, 6, m, mm2, 3m, 4mm, or 6mm). Thus, polarity is required for pyroelectric behaviour. Determining the pyroelectric coefficient may be done two ways - either measuring the pyroelectric current or the pyroelectric charge. Both techniques will be described. 

A ferroelectric is formally defined as a pyroelectric material that has a reversible, or switchable , polarisation.Thus, for a material to be ferroelectric, the compound must be polar, i.e. must possess a permanent dipole moment, and must be capable of having this moment 

This section is divided into four parts. Each part describes a specific NCS property, the history of the phenomena, and provides details on the measurement as well as an interpretation of the resulting data. 

---