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Achievements 2012 - 2018
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A new relaxor family Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 with the largest known range of relaxor behaviour up to now is synthe­sized and studied for the first time:

  • High value ECE at field-induced phase transitions in compositions with weak stability relaxor state,
  • Relation of local energy landscape and stability of ferroelectric state in appearance of relaxor state,
  • New interpretation of dielectric dispersion (instead of Vogel-Fulcher law),
  • Evaluation of Burns temperature.

Phase diagram of Na1/2Bi1/2TiO3-BaTiO3 solid solutions above morphotropic phase boundary:

  • Three types of concentration range with different nature of phase transition have been found,
  • High tetragonality of lattice with increasing concentration of Na1/2Bi1/2TiO3 is found,
  • Contribution to interpretation of phase transitions in pure Na1/2Bi1/2TiO3.

Electrocaloric effect

  • on example of Na1/2Bi1/2TiO3 it is shown that using of Maxwell relations for indirect determination of electrocaloric effect is incorrect due to complex nature of polarisation.

Studies of crystallographic symmetry in Na1/2Bi1/2TiO3 based compositions:

  • First time octahedral tilt system a+b+c+ is found in real material, Na1/2Bi1/2TiO3-CdTiO3 solid solutions.
  • Well expressed structural phase transition in Na1/2Bi1/2TiO3-CaTiO3 solid solutions with small concertation of CaTiO3 allows better understanding of the nature of phase transitions in pure Na1/2Bi1/2TiO3.

Luminescence in lanthanide doped Na1/2Bi1/2TiO3

  • Studies of luminescence in Er doped Na1/2Bi1/2TiO3 allow to conclude that poled state is more symmetric comparing with depoled one.
  • Local environment around Er3+ ions due to disordered distribution of Na1+/Bi3+ ions vary in quasi continuous way, what is reflected in dependence of luminescence wavelength on excitation wavelength.

The Effects of 3d Admixtures on Properties of Ferroelectric PLZT8/65/35 Ceramics:

  • Admixtures may ameliorate as well as restrain relaxor characteristics,
  • Mn, Fe, Co, Ni, and Cu dopants are related to several competing factors affecting polarization: Jahn-Teller effect, change of the concentration and orientation of polar nano-regions, the Maxwell-Wagner polarization, change of the concentration of vacancies in A and/or O sub-lattices.

Grain morphology

  • Characteristic bimodal grain morphology is found in NBT-based solid solutions, which is related with anomalous grain growth mechanism.
  • The role of Bi-nonstoichiometry on depressing of grain growth mechanism is clarified. The possibility to vary content of Bi in NBT is very restricted.
  • Lanthanides (Er, Yb) efficiently replace Bi from A-sites of ABO3 perovskite lattice.

Potassium-sodium niobate solid solution based ferroelectric ceramics

  • Improved ceramics using a wide variety of oxides as sintering-promoting additives. Addition of manganese dioxide (MnO2) promotes densification as well as improves dielectric, ferroelectric and piezoelectric properties.