posted on 2021-06-16, 15:07authored byVladimir
A. Morozov, Svetlana M. Posokhova, Sergey Ya. Istomin, Dina V. Deyneko, Aleksandra A. Savina, Boris S. Redkin, Nikolay V. Lyskov, Dmitry A. Spassky, Alexei A. Belik, Bogdan I. Lazoryak
The influence of different synthesis
routes on the structure and
luminescent properties of KTb(MoO4)2 (KTMO)
was studied. KTMO samples were prepared by solid-state, hydrothermal,
and Czochralski techniques. These methods lead to the following different
crystal structures: a triclinic scheelite-type α-phase is the
result for the solid-state method, and an orthorhombic KY(MoO4)2-type γ-phase is the result for the hydrothermal
and Czochralski techniques. The triclinic α-KTMO phase transforms
into the orthorhombic γ-phase when heated at 1273 K above the
melting point, while KTMO prepared by the hydrothermal method does
not show phase transitions. The influence of treatment conditions
on the average crystallite size of orthorhombic KTMO was revealed
by X-ray diffraction line broadening measurements. The electrical
conductivity was measured on KTMO single crystals. The orthorhombic
structure of KTMO that was prepared by the hydrothermal method was
refined using synchrotron powder X-ray diffraction data. K+ cations are located in extensive two-dimensional channels along
the c-axis and the a-axis. The possibility
of K+ migration inside these channels was confirmed by
electrical conductivity measurements, where strong anisotropy was
observed in different crystallographic directions. The evolution of
luminescent properties as a result of synthesis routes and heating
and cooling conditions was studied and compared with data for the
average crystallite size calculation and the grain size determination.
All samples’ emission spectra exhibit a strong green emission
at 545 nm due to the 5D4 → 7F5 Tb3+ transition. The maximum of the integral
intensity emission for the 5D4 → 7F5 emission under λex = 380 nm
excitation was found for the KTMO crashed single crystal.