Ceramic and Dielectric Properties of Lead Metaniobate Electrical Ceramics

The effect of firing temperature and time on the weight loss, fired porosity, and dielectric properties of lead metaniobate was investigated. The amount of lead oxide lost was found to be a linear function of firing time and in addition increased rapidly as the firing temperature was increased. Specimens fired for 30 minutes at temperatures below 1275°C. had weight losses of less than 1% based on the amount of available PbO present, whereas specimens fired for the same length of time at temperatures greater than 1275°C. had weight losses up to 3.5%. Both a minimum and a maximum point were found in the fired porosity curve of lead metaniobate in the temperature range 1200° to 1350°C. When firing for 30 minutes, the minimum point occurred at about 1225°C. with a porosity value of 8% and the maximum point at 1300°C. with a porosity of 18%. The effect of porosity and weight loss on the dielectric properties of lead metaniobate is presented. The effect of replacing up to 0.7 mole fraction of the lead ion in lead metaniobate by cadmium was investigated. Cadmium additions lowered the Curie temperature and diluted the ferroelectric properties of lead metaniobate.