ANOMALOUS DIELECTRIC, PIEZOELECTRIC AND ELASTIC PROPERTIES OF ORTHORHOMBIC NICKEL ZIRCONIUM BIS(NITRILOTRIACETATE)-CENTER-DOT-8.5-HYDRATE, NIZR[N(CH2COO)3]2-CENTER-DOT-8.5H(2)O

Large single crystals of optical quality of nickel zirconium bis (nitr ilotriacetate).8.5 hydrate (space group C222(1)) have been grown from aqueous solutions. Complete elastic, thermoelastic and piezoelastic te nsors were determined by the aid of ultrasonic methods. In addition, t he indices of refraction, the tensor of thermal expansion, dielectric and piezoelectric constants have been studied. Most physical propertie s investigated show a strong anisotropy. E.g. the relative dielectric constants epsilon(33) and epsilon(11) have values of 335 and 7, respec tively. The static piezoelectric constant d(312) surmounts 750 pC/N (b y more than a factor of 300 larger than d(111) Of alpha-quartz), where as d(123) remains as low as 4 pC/N. Anomalous features are the sharp b end of the temperature dependence of epsilon(33) at about 287 K, and, above 280 K the increasing attenuation of transversal ultrasonic waves propagating along [100] with displacement vector parallel to [010] an d vice versa. These waves are related to the elastic constant c(66) Th e anomalies and the large values of epsilon(33) and d(312) hint at a h igher-order ferroelectric transition.