Structural Characterization of Orthorhombic and Rhombohedral Lead Meta-Niobate Samples

Abstract

The meta-stable orthorhombic phase of lead meta-niobate (PbNb 2 O 6 ), as obtained by quenching, is piezoelectric, but difficult to prepare in pure state as a few competing phases like the non-piezoelectric rhombohedral PbNb 2 O 6 tend to form during the preparation. However, it can have an attractively high Curie temperature above 570 • C. High Curie temperature piezoelectric sensors are desirable for imaging and other applications in certain industrial and research sectors. Presently, both phases have been synthesized as single phase samples as shown here from structural Rietveld analysis of their XRD. Characterization of both compounds by FTIR and XRD have been carried out and presented.

Dielectric Properties of RhombohedralPbNb2O6

“…This peak3 peak (at ∼684 ∘ C) is rather sharp. This peak2 matches, with respect to temperature, the ferroelectric to paraelectric transition [16] of orthorhombic PbNb 2 O 6 , Figure 4, presently observed low intensity peaks, marked in the present figure, got removed.…”

“…confirming its presence as an impurity of much lower value of peak2 (height at peak2), compared to the value of max [16] of the ferroelectric PbNb 2 O 6 , as detailed in Table 1 Figure 3 shows temperature dependence of the imaginary part of the dielectric constant ( ), during heating from room temperature to 700 ∘ C for different measuring frequencies in the range 1 kHz to 5.5 MHz for PNS. For 1 kHz graph, increases sharply in the temperature range of 450 ∘ C to 650 ∘ C and then decreases with the increase of temperature, in our study being up to 700 ∘ C. Inset shows to be practically constant with temperature up to 450 ∘ C at high frequencies (1 MHz to 5.5 MHz).…”

“…Slow ( ) cooling (from temperatures like 1270 ∘ C) leads [10,11] to PNS, rhombohedral PbNb 2 O 6 , which is not ferroelectric; ruling out piezoelectric properties and piezoelectric applications. So, most R & D efforts have been concentrated on orthorhombic PbNb 2 O 6 [1][2][3][4][5][12][13][14][15][16][17][18][19][20][21]. Even the real part ( ) and imaginary part ( ) of the dielectric constant of the nonferroelectric PbNb 2 O 6 with rhombohedral phase have rarely been reported [16,22].…”

“…No analysis of its dielectric data has yet been made to study paraelectric and other physical properties in detail, although rhombohedral PbNb 2 O 6 is a dielectric material in its own right. So, an analysis of its dielectric data [23] has been carried out in this work, after preparing rhombohedral PbNb 2 O 6 in practically pure state, with X-ray Rietveld confirmation of the structure and impedance spectroscopy (IS) covering 20 Hz to 5.5 MHz at different values the sample temperature ( ) up to 700 ∘ C. [16]. Firing in compact pellet form and grinding plus repelletizing before each firing improved sample quality.…”

“…So, most R & D efforts have been concentrated on orthorhombic PbNb 2 O 6 [1][2][3][4][5][12][13][14][15][16][17][18][19][20][21]. Even the real part ( ) and imaginary part ( ) of the dielectric constant of the nonferroelectric PbNb 2 O 6 with rhombohedral phase have rarely been reported [16,22]. No analysis of its dielectric data has yet been made to study paraelectric and other physical properties in detail, although rhombohedral PbNb 2 O 6 is a dielectric material in its own right.…”