MS13-P16 Piezoelectric phase transition in KSrVO4 investigated using the Aeris diffractometer Jan Gertenbach (Malvern Panalytical, Almelo, Netherlands (Holland, Europe)) Gwilherm Nénert (Malvern Panalytical, Almelo, Netherlands (Holland, Europe))email: jan.gertenbach@panalytical.comThe rich crystal chemistry of AIBIIXO4 (AI = alkali ion, BII = alkali-earth ion, X = P, V, As) leads to numerous polymorphic phases that have related structural families, such as olivine (e.g. LiMnPO4), arcanite (β-K2SO4), glaserite, tridymite, α-K2SO4, β-Na2SO4 and γ-Na2SO4 [1]. Among the various families (X = P, V, As), the phosphates have been most widely studied. In addition to their interesting crystal chemistry behaviour, research on this family of materials is mainly driven by their ferroelectric-, and ferroelastic properties as well as possible applications as phosphors for LEDs [1].
In recent years, we have investigated several structural combinations of the AIBIIVO4 type [2] and a new crystal type within this family was identified, namely a form of NaSrVO4 that is isostructural to larnite [2]. In this work, we continue our exploration of the AIBIIVO4 family by investigating the composition of KSrVO4. While NaSrVO4 crystallizes in the P21/n space group, divergent results are reported for KSrVO4. Single crystal work suggests Pnma symmetry [3], but powder diffraction studies show evidence for P212121 symmetry with distinct reflections present that are not consistent with Pnma symmetry[3]. These contradictory results prompted us to study the structural composition of the compound as a function of temperature.
Using the Aeris benchtop diffractometer equipped with the BTS 500 non-ambient chamber, the crystal structure of KSrVO4 was studied in the 25-500°C range. At room temperature the structure is best described as having P212121 symmetry, allowing for piezoelectricity in this material. By increasing the temperature, it is possible to observe a phase transition to Pnma symmetry. This phase transition appears to be related to the piezoelectric nature of the material and its associated spontaneous strain.
This work reports on the first purely gyrotropic phase transitions in the AIBIIVO4 family.

[1] Isupov, V.A. (2002) Ferroelectrics, 274(1), 203 and Choi, S., Yun, Y. J., Kim, S.J. & Jung, H.-K. (2013) Optical Lett., 38, 1346

[2] Nénert, G., O’Meara, P. & Degen T. (2017) Phys. Chem. Minerals, 44, 455 and Nénert, G. (2017) Z. Kristallogr. 232(10), 669

[3] Klement, R. & Kresse, P. (1961) Z Anorg Allg Chem, 310, 53 and Azrour, M., El Ammari, L., Le Fur, Y. & Elouadi B. (2000) Materials Research Bulletin, 35, 263

Keywords: phase transitions, spontaneous strain, benchtop XRD