Modified ceramics (Pb_1−xCa_x)[(Mn_0·5W_0·5)_0·10Ti_0·90]O₃ have been fabricated forx=0, 0·05, 0·10 and 0·15 by high temperature solid state reaction technique. XRD, SEM, DTA and electrical studies of the sample withx=0·10 have been performed. These studies show that the sample is homogeneous single phase perovskite type with tetragonal structure. The phase transition occurs at 330°C. Electrical behaviour of other samples have also been investigated as a function of frequency (1 kHz to 1 MHz) and temperature (26°C to 300°C). The samples withx=0·05 and 0·10 have low loss, low dielectric constant, and show negligible pyroelectric effect. The sample withx=0·15 has minimum values ofɛ and loss which are temperature independent up to about 200°C. It also shows good pyroelectric behaviour. Hence it may be of use in pyroelectric infrared sensors.

Ceramics (Pb_0·75Ca_0·25)[(Ni_1/2W_1/2)_yTi_1−y]O₃ fory = 0 ·05, 0·10, 0·15 and 0·30 have been prepared using high temperature solid state reaction method. X-ray analyses show that these materials are of single-phase perovskite type tetragonal structure. To solve inaccuracy in finding para-ferroelectric phase transition temperatureT_c(ε_max), we have carried out the analyses of the data using a computer program. The role of Ni and W as modifiers on structural and electrical (dielectric and pyroelectric) properties is discussed in terms of the usefulness of these materials. Results indicate that ceramic Pb_0·75Ca_0·25Ni_0·25W_0·025Ti_0·95O₃ is a good candidate for pyroelectric applications.