Structural phase transition in Zn 1.98 Mn 0.02 P 2 O 7 : EPR evidence for enhanced line broadening and large zero-field splitting parameter in high temperature phase

Zn 1.98 Mn 0.02 P 2 O 7 was synthesized by the wet chemical route. The purity of the phase and the oxidation state of manganese ion were investigated by x-ray diffraction (XRD) and electron paramagnetic resonance (EPR). Structural phase transition in α-Zn 2 P 2 O 7 was investigated by high-temperature XRD (HTXRD), differential scanning calorimetry (DSC), and EPR studies. There is a distinct signature of phase transitions between 390 and 400 K in our powder sample by EPR and HTXRD. There was a sharp reduction in the volume of unit cell, while going from alpha to beta phase; with discontinuity in 405 K, which confirmed the transition to be of first order. Similarly, the effect of temperature on zero-field splitting parameter ( D ) also showed that there is a sudden jump (discontinuity) in the value at around 400 K (phase transition temperature) confirming the transition to be of first order. DSC studies corroborated these findings.