Abstract
We have investigated in situ a continuous transition between the orthorhombic and tetragonal phases in perovskite-structured La
0.63(Ti
0.92,Nb
0.08)O
3 by three X-ray powder diffractometers with different Δ
d/
d resolutions of 0.03%, 0.06% and 0.10%. The
d and Δ
d denote the
λ/(2·sin
θ) and peak width where
λ and
θ are wavelength of X-ray and Bragg angle. Only the highest-resolution diffractometer of Δ
d/
d=0.03% was able to detect the peak splitting between 400 and 040 reflections in the temperature range of 327–339°C. It was found that the accuracy of the transition temperature is considerably improved with decreasing of Δ
d/
d value. The maximum temperature where the peak splitting between 400 and 040 reflections is detectable increases, while the transition temperature determined by a power law decreases with decreasing of Δ
d/
d value.