Dielectric and electrical properties of LiNbO₃ ceramics

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Chemical formulae obtained by analysis and proposed formulae in good agreement with the model of Iyi ([Li_1−xNb_x/5(V_Li)_4x/5] NbO₃) [13], with different stoichiometries of LN (where □ denotes the empty Li-site).

Samples	Li/Nb	Experimental formulae	Proposed formulae
S1	1.007	Li1.0064Nb0.999O3	[Li0.0064Li][Nb]O3
S2	0.971	Li0.976Nb1.005O3	[Li0.976Nb0.005□0.019][Nb]O3
S3	0.948	Li0.957Nb1.009O3	[Li0.957Nb0.009□0.034][Nb]O3
S4	0.911	Li0.925Nb1.015O3	[Li0.925Nb0.015□0.06][Nb]O3

Fig. 1 XRD patterns of samples S₂ (x = 0.025), S₃ (x = 0.045) and SEM micrograph (inset) of sample S₂.

Table 2 Values of cell parameters a, c, ratio c/a and cell volume of samples S₁, S₂, S₃ and S₄.

Li/Nb		a (Å)	c (Å)	c/a	Cell volume (Å^3)
S1	1.007	5.1402	13.8577	2.6959	317.06
S2	0.971	5.1425	13.8696	2.6970	318.89
S3	0.948	5.1531	13.8734	2.6922	319.04
S4	0.911	5.1517	13.8705	2.6924	318.80

Fig. 2 Equivalent electrical RC circuit for grain, and grain boundary and electrode–electrolyte interface effects.

Fig. 3 Variation of Nyquist plots of samples (a) S₁, (b) S₂ and (c) S₄ at different temperatures.

Fig. 3 (Continued).

Fig. 4 Ac conductivity as a function of frequency at different temperatures for all samples (a) S₁, (b) S₂, (c) S₃ and (d) S₄.

Fig. 4 (Continued).

Table 3 Values of critical exponent n₁ and n₂ for S₁, S₂, and S₃ at different temperatures.

Samples	Temperature (°C)	n1	n2
S1	400	0.02	1.18
S1	800	0.03	1.28
S1	900	0.01	1.66
S2	300	0.024	1.71
S2	500	0.023	1.39
S2	900	0.016	1.33
S3	400	0.05	1.02
S3	500	0.028	1.09
S3	800	0.018	1.74

Table 4 Values of E_a (activation energy) and σ₀ (pre-exponential factor) before and after the temperature threshold of samples S₁, S₂, S₃ and S₄.

Samples	Li/Nb	Before the threshold temperature		1000/T	After the threshold temperature
		Ea (eV)	σ0 (Ω^−1 cm^−1)		Ea (eV)	σ0 (Ω^−1 cm^−1)
S1	1.007	0.78	0.13	1.15	1.20	27.2
S2	0.971	0.85	0.97	1.07	1.23	80.8
S3	0.948	0.84	0.71	1.08	1.25	123.6
S4	0.911	0.88	1.15	1.20	1.24	88.1

Fig. 5 Variation of static conductivity vs the 1000/T for the samples (a) S₁ and (b) S₂.

Fig. 6 Variation of static conductivity vs the 1000/T for the samples (c) S₃ and (d) S₄.