SYNTHESIS OF COMPLEX LANTHANUM AND CALCIUM TITANATES WITH A PEROVSKITE STRUCTURE AND THEIR ELECTRIC PROPERTIES STUDIED AT HIGH TEMPERATURES

摘要

Phase formation in the CaTiO_3-La_2O_3 system in the concentration range 0-40 mol. percent La_2O_3 is revisited. Conductivity, dielectric constant, and dielectric loss are measured in the temperature range of 5-600 deg C, and electric strength and the temperature coefficient for dielectric constant (TCepsilon) of perovskite phase in the CaTiO_3-La_2O_3 system are determined. The ceramic materials studied have a low dielectric loss depending but slightly on temperature [tan delta = (1-6) X 10~(-4)], a high dielectric constant (epsilon = 30-120), and a TCepsilon varying from -1480 X 10~(-6) deg~(-1) to +10,500 X 10~(-6) deg~(-1) with composition; the zero point for TCepsilon is identified at 23 mol. percent La_2O_3.