EFFECT OF LANTHANA AND NIOBIA ADDITIVES ON THE PHYSICAL PROPERTIES OF BARIUM TITANATE CERAMICS

Abstract

Barimn titanate has been used as a multilayer ceramic capacitor due to its high dielectric constant and low dielectric loss. The aim of the present work is to investigate the effect of lanthanmn oxide (La 2 03) and niobium oxide (Nb 2 0 5) additives on the physical properties of the ceramic BaTi 0 3 . Samples were prepared, using the ceramic technique, to obtain the composition BaTi0 3 -La 2 03 -Nb 2 05 (with Nb 2 05 =O.lwt% and La 203 =0.0,0.1, 0.2,0.3 and 0.4). The investigation included the study of the effect of La substitution and temperature on various properties. The structure of the samples have been confinned by X-ray diffraction showing that beside the main tetragonal phase, there is a new phases due to the inhomog neity of the dopants during preparation method. The lattice parameter, the density, X-ray density and porosity are detennined as a functions of composition. • The dielectric constant have been measured in a wide range of temperature from room temperature to 200 o C for all compositions at constant frequency 1 KHz, also dielectric loss have been measured at the same frequency (1 KHz) from room temperature to 160 o C. D. C. Resistivity have been measured in the temperature range 60-200 °C. Thermal conductivity have been measured under vacumn from room temperature to 200 °C. The main conclusions can be smnmarized as follows: 1- The axial ratio (cIa), at room temperature, decreases initially with increasing lanthamun content up to X= 0. 2 and then increases, tllis is due to La ions initially enter the lattice replacing Ba ions causing an increase in a parameter,