Abstract
Ceramics of binary systems solid solutions (1 – x)NaNbO3 – xCa2Nb2O7 and (1 – x)NaNbO3 – xSr2Nb2O7 with non-isostructural extreme components were prepared by the solid-phase reactions technique with the following sintering using conventional ceramic technology. It was found that ceramics with x ≤ 0.2 have a perovskite structure. Layered type of structure predominates in the concentration range 0.2 <x ≤ 1. Phase diagrams of both systems at room temperature have been determined in the perovskite area. It was shown that this area contains two concentration regions with the different crystal structures and the morphotropic phase boundary between them. Microstructure and dielectric characteristics of selected solid solutions were investigated. The influence of technological regulations, such as mechanical activation and variation of sintering temperatures, on the formation of the microstructure and dielectric characteristics was studied for the individually selected concentrations (x = 0.1 and x = 0.25). Dielectric characteristics of ceramics revealed the presence of the Maxwell-Wagner polarization and its corresponding relaxation in the solid solutions (1 – x)NaNbO3 – xCa2Nb2O7 at x > 0.20.
Highlights
The perovskite-like layer structured (PLS) ferroelectrics with a formula of AnBnO3nþ2 have received considerable attention because of their wide ranging properties
It was found (Figure 1) that solid solutions based on NaNbO3 with a perovskite (P) structure are formed in the concentration range 0.00 x 0.20 in both systems
It can be seen that NCN25 PLS compound is well structured, while NaNbO3 – xSr2Nb2O7 (NSN) system structure was formed only at x 1⁄4 0.3
Summary
The perovskite-like layer structured (PLS) ferroelectrics with a formula of AnBnO3nþ have received considerable attention because of their wide ranging properties. CN is considered as a promising compound for non-linear optics [3], laser technology [4], highly active photocatalyst for water splitting [5, 6], design a multifunctional optical storage device [7, 8] Both the CN and SN demonstrate mild piezoelectric properties (d33 < 10 pC/N) with extremely high Curie temperatures (~1800 K and ~1600 K, respectively) [9, 10]. This work aimed to investigate phase composition, crystal structure, microstructure and dielectric characteristics of NCN and NSN systems and to evaluate the influence of technological regulations on the macroresponces of the obtained solid solutions
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