NEODYMIUM TITANATE (ND2TI2O7)CERAMICS

Neodymium titanate ceramics have been prepared by the mixed oxide route. Specimens were sintered in air at temperatures in the range 1300 to 1500-degrees-C. Fired densities were sensitive to sintering temperature with the highest densities for undoped specimens (approximately 95% theoretical) being achieved at 1375 to 1400-degrees-C. The microstructures of such specimens exhibited abnormal grain growth; tabular to lath-shaped grains up to 100 mum in size. Doping with Nb2O5 controlled grain growth, but at dopant levels greater than 1 mole % an increasing amount of second phase was formed. Undoped Nd2Ti2O7 ceramic has a relative permittivity of approximately 35 and a positive temperature coefficient of capacitance of 270 ppm/degrees-C (for the range 25 to 150-degrees-C). TEM studies revealed the presence of fine domain structures which are twinned, confirming the ferroelectric nature of Nd2Ti2O7.