| Abstract Scope |
In this study, the effect of the type and extent of A-site doping with divalent alkaline earth cations on the phase transformation and thermal properties of RENbO<sub>4</sub> (RE = La, Dy) was investigated. Powder samples of La<sub>1-x</sub>M<sub>x</sub>NbO<sub>4-δ</sub> (M = Mg, Ca, Sr, Ba; x=0 to 0.02, in steps of 0.01) and Dy<sub>1-y</sub>Mg<sub>y</sub>NbO<sub>4-δ</sub> (y = 0 to 0.05, in steps of 0.01) were synthesized by the stearic entrapment method. Specific heat capacity from differential scanning calorimetry, and high temperature X-ray diffraction were used to understand the phase transformations and thermal properties up to 1500°C. All the materials exhibited second order transformation, and aliovalent doping increased the transformation temperature. The t-DyNbO<sub>4</sub> phase also showed order-disorder transformations at high temperatures, which decreased with increasing Mg<sup>2+</sup> concentrations. Key results on change in lattice parameters, effect on the phase transformation, and thermal expansion will be presented as a function of composition and temperature. |